The present invention relates to a method of detecting whether there is a leak in a building's water system, and if so the height or location thereof, and a product for carrying out the method. This method will be of most use for finding out if a system has a leak which cannot be detected by visual inspection, or to determine how fast a system is leaking if or when a leak is found.

The water system in a building will typically be one of two types—a ‘unvented’ or ‘pressurised’ system or a vented system. A pressurised system is a water system held at mains pressure, with water either heated on demand by a combi-boiler or heated and held in a pressurised ‘unvented’ hot water cylinder. Such systems contain an expansion vessel or ‘EV’ which contains a bladder of air which is compressed to a greater or lesser extent as the pressure in the system increases or decreases.FIG. 1illustrates a simple vented system. A ‘vented’ system is instead fed from a cold water tank or ‘header tank’—usually in a loft of the building, which is supplied with mains water, but is itself only loosely covered and held at atmospheric pressure. In the vented system, water is then fed from the header tank to the hot water system and in some cases to cold water taps. Other cold taps, including in nearly all cases the kitchen cold tap, are instead supplied directly from the mains in case bacteria breed in the header tank. The pressure in the parts of the system fed by the header tank is simply a product of the weight of water above them. This pressure, as caused by the weight of water, is called the ‘head’.

If there is a leak in either of these systems, the water that leaks can cause damage to the structure or furnishings of the building. The present invention therefore seeks to provide a method and apparatus for detecting the presence of leaks and preferably for locating the position or height of said leak within the building/pipework if detected.

Known methods for leak detection include using the household water meter—this typically only detects larger leaks. It is done by closing all taps etc., so that there is no intended use of water, recording the reading of the water meter, waiting for a certain period of time, such as 15 minutes, and then checking the meter reading again. If the meter has recorded water use during the test, it might be due to a leak. Another test, for pressurised parts of a water system, involves shutting off the mains water supply (e.g. by closing the building's stop cock), closing all taps etc., and seeing whether the pressure within that pressurised part of the water system falls.

These techniques are well known in the industry, and there are more detailed versions too, e.g. for factoring in how changes in temperature might affect the pressure reading etc. However, as most buildings will depressurise somewhat over time, this then begs the question; when should we be worried?—i.e. is this depressurisation the sign of a serious leak or is it merely the result of the system settling, and how do we differentiate between the two?

The present invention seeks to provide a readily accessible and effective approach for detecting, and perhaps locating, leaks in the water system, and for providing an indication to allow determination as to whether the leak could be a concern.

According to a first aspect of the present invention there is provided a method for testing for a possible water leak in at least a part of a water system, comprising:closing all known water usage taps within the part of the water system to be tested;closing at least one stop cock or valve of the water system to isolate the part of the water system from its replacement water source (or sources), and any external replacement pressure source (or sources); and thena) detecting a first pressure P0within the isolated part of the water system at a sensor connected to the part of the water system, waiting a period of time t and then detecting a second pressure P1within the isolated part of the water system at that sensor; andb) releasing a volume of water VRfrom the water system out of the isolated part of the water system via a vent in the isolated part of the water system, before then closing the vent, step b) further comprising detecting the pressures either side of that release at that sensor;the method thus recording a) a pressure loss in the system over a period of time t caused by an unknown leak volume of water VLescaping the system and b) a pressure loss in the system caused by an approximately known or measurable volume of water released from the system;the method further comprising using the pressure drop caused by the approximately known or measured volume of water VRto enable an estimate of the relationship between change in pressure in the system and the volume of water released to be established, and based on the relationship between the change in pressure and the known release volume, calculating an estimate of the actual volume of the unknown water loss volume based upon the recorded pressure loss in the system in the known period of time t.

This method can also be used for liquid systems other than water.

If the water is to be measured as it is released, it can be vented into a measuring device. The volume of water may then be known by measuring the amount of water released with the measuring device. As an example, this may by a cup in a sink below a tap, the volume being measured by either measuring the volume or weighing it and converting that weight into a volume (as the volume of the liquid per unit mass/weight is likely to be known). Using a measuring cup is perhaps the easiest approach. More complex fixed volume release vents could also be used, however, or a fixed time of release may be used to allow an approximation of the volume released for a given pressure and vent size.

Step a) may be before or after step b).

One of the two detected pressures of step a) may be one of the two detected pressures of step b). For example, if step a) is carried out before step b), then the second pressure detected in step a) may be the first pressure detected in step b)—i.e. the pressure before the release of the water. Alternatively if step b) is carried out before step a), then the second pressure detected in step b) may be the first pressure detected in step a)—i.e. the pressure after the release of the water and at the start of the period of time t.

The method may further offer a conclusion regarding that calculated estimate volume, wherein if that calculated estimate volume is greater than a predetermined value greater than 0 it is determined that there is a possible water leak needing investigation.

In another aspect of the present invention there is provided a method for testing for a possible water leak in at least a part of a water system, comprising:closing all known water usage taps within the part of the water system to be tested;closing at least one stop cock or valve of the water system to isolate the part of the water system from its replacement water source (or sources), and any external replacement pressure source (or sources); and thena) detecting a first pressure P0within the isolated part of the water system at a sensor connected to the part of the water system, waiting a period of time t and then detecting a second pressure P1within the isolated part of the water system at that sensor; andb) releasing a volume of water VRfrom the water system out of the isolated part of the water system via a vent in the isolated part of the water system, before then closing the vent and detecting a third pressure P2within the re-isolated part of the water system at that sensor;the method further comprising:calculating an approximate leaked water loss VLby using the following equation:
VL=VR*P2(P0−P1)/(P0(P1−P2)).
Here the pressure readings are absolute pressures. Where they are gauge pressures, the formula may be substituted with the following:
VL=VR*(P2 gauge+PAtmospheric)*(P0−P1)/((P0 gauge+PAtmospheric)*(P1−P2))

The released volume VRmay again be measured or approximately known, as before.

The method may make a conclusion such as where if VLis greater than a predetermined value greater than 0, it is determined that there is a possible water leak needing investigation.

In some embodiments the period of time t is a period of time exceeding 2 minutes. For larger leaks, this may be a shorter period of time—say 1 minute. However, such larger leaks are more likely to be visually detectable.

In some embodiments the time between taking the second and third pressures P1and P2is less than 20 seconds. However, it can be longer if time t is much longer than 2 minutes.

Preferably the period of time t is more than 2 minutes. In a preferred embodiment it is between 3 and 5 minutes, or less than 10 minutes. The most preferred time is around 5 minutes, although a wait of 3 minutes is fine too, but it may reduce accuracy a bit. The time can be longer, however, with the invention still working, although a limiting factor can be ensuring that the system doesn't depressurise completely, or at least that it doesn't depressurise to such an extent that letting out the fixed volume of water then causes it to depressurise completely.

The time can also be varied further, especially if the pressure drop is rapid—in which case the wait time might be reduced to 20-30 seconds so that the system doesn't completely depressurise. This could be arranged to occur automatically if a pressure reduction rate is measured.

In the case instead of the pressure drop being slower, the wait time could be extended—to more than 5 or 10 minutes—so that errors in the pressure measurements have less effect on the calculation.

Preferably the time between taking the second and third pressures P1and P2is between 1 and 12 seconds. In a preferred embodiment it is about 10 seconds.

In some circumstances, 1 second can be a bit too fast—there can be an instantaneous spike in pressure as water is released which might be accidentally recorded if only a 1 second interval is used, so it is better to wait a little longer—say 3 seconds or more, or to take a couple of readings to see if a spike has occurred. In most circumstances an interval of 5 to 10 seconds is preferred.

Generally the time t between taking the first and second pressures P0and P1is significantly longer than the time between taking the second and third pressures P1and P2—preferably it is at least 10 times longer, and more preferably at least 20 times longer. Most preferably it is at least 30 times longer.

Although we recite that at least one stop cock or valve is shut, it is to be understood that every access point to replacement water in the part of the system being tested is closed, and commonly this is just a single stop cock or valve.

Preferably the released volume of water VRis less than 80 ml, and more preferably less than 50 ml. In one embodiment it is about 43 ml. In another it is about 25 ml of water. It is helpful if the volume of water is large enough to be easily measurable so as to give a more accurate idea of leak rate (i.e. ideally greater than 5 ml, and more preferably greater than 10 ml), but yet still small enough not to totally depressurise the system. In preferred embodiments, on small household water systems, with no expansion vessels, this would be below 10 ml, whereas on a larger water system, as much as 50 ml may be appropriate.

Preferably the sensor is located at or near the bottom of the part of the water system being tested. It may be attached, for example, to a washing machine attachment point, or similar, or to a tap.

The vent for releasing the volume of water VRmay be a tap within the isolated part of the water system, such as a basin tap or a kitchen tap. Preferably it is near the sensor to facilitate taking the second and third pressure readings in quick succession either side of the release of the volume of water VR. In a preferred embodiment it is attached to the same test assembly as the sensor so that the test assembly, when attached to an attachment point of the water system, attaches both a vent for water release and a sensor.

Preferably the method calculates the rate of water release by dividing VLby t. By detecting how fast it is leaking, the leak rate (VL/t), a decision can be taken as to whether the leak needs fixing. For example, a very slow leak may just be the system settling down, whereby no action is needed. Preferably a need to fix a leak is identified when the determined leak rate exceeds a threshold, such as more than 0.1 ml per minute, or more than 1 ml/min or perhaps 2 ml/min.

Preferably this first aspect is for testing for leaks in a pressurised water system. For example, the pressure may be in excess of the head of the water within the part of the water system being tested—for example by it usually being connected to the mains—the stop cock or valve being the mains isolator stop cock.

Preferably the method also includes attaching the pressure sensor—in advance of closing the mains stop cock, although a pressure sensor may be already attached to the water system, whereby such an attachment is not essential.

In a variant to the above, multiple pressure readings are taken before and potentially after the release of the volume of water, and then the or each curve is extrapolated forwards (and potentially backwards) for the resultant trace(s) such that the second and third pressure values representing an instantaneous pressure change resulting from the controlled water loss can be determined. This approach can give a more accurate leak volume determination as it removes some errors arising in the calculation or the test. For example, errors can arise due to the non-zero duration of the water release, the continuing pressure losses arising due to the pre-existing “leak” during the interval between the pressure readings either side of the water release, and pressure spikes arising due to valve opening or closing processes.

According to this aspect of the present invention there is provided a method for testing for leaks in at least a part of a water system, comprising:closing all known water usage taps within the part of the water system to be tested;closing at least one stop cock or valve of the water system to isolate the part of the water system from its replacement water source, and any external replacement pressure sources; and then:a) detecting pressures within the isolated part of the water system at a sensor connected to the part of the water system at predetermined intervals for a period of time t long enough to obtain a sequence of pressure readings; and b) releasing a volume of water VRfrom the water system out of the isolated part of the water system via a vent in the isolated part of the water system, before then closing the vent, step b) further comprising detecting pressures either side of that release at that sensor.

With the pressure and time/volume data collected the method recorded a) a pressure loss sequence in the system over a period of time t caused by an unknown leak volume of fluid VLescaping the system and b) a pressure loss in the system caused by an approximately known or measurable volume of fluid escaping the system. The approximately known or measurable volume can be measured as before. Again, therefore, the method may use the pressure drop caused by the approximately known volume of fluid VRto enable an estimate of the relationship between change in pressure in the system and the volume of fluid released to be established, and based on the relationship between the change in pressure and the known release volume, calculate an estimate of the actual volume of the unknown fluid loss volume based upon the recorded pressure loss in the system in the known period of time t.

The method may further offer a conclusion regarding that calculated estimate volume, wherein if that calculated estimate volume is greater than a predetermined value greater than 0 it is determined that there is a possible water leak needing investigation.

As before, the approximately known volume of water may be known by measuring the amount of water released, e.g. by releasing it into a measuring cup.

Furthermore, step a) may be before or after step b).

Yet further, one of the two detected pressures of step b) may be one of the detected pressures of step b). For example, if step a) is carried out before step b), then a final pressure detected in step a) may be the first pressure detected in step b)—i.e. the pressure before the release of the water. Alternatively if step b) is carried out before step a), then the second pressure detected in step b) may be the first pressure detected in step a)—i.e. the pressure after the release of the water and at the start of the period of time t.

As a further alternative, the method may instead determine a gradient or decay rate of the pressure during the sequence of pressure readings, and then use that decay rate, and the pressure drop caused by the release of the approximately known volume of fluid VRto enable an estimate of the water loss from the leak VLto be determined.

According to a similar approach there is provided a method for testing for leaks in at least a part of a water system, comprising:closing all known water usage taps within the part of the water system to be tested;closing at least one stop cock or valve of the water system to isolate the part of the water system from its replacement water source, and any external replacement pressure sources; and then:a) detecting pressures within the isolated part of the water system at a sensor connected to the part of the water system at various intervals for a period of time t long enough to obtain a sequence of pressure readings; and thenb) releasing a volume of water VRfrom the water system out of the isolated part of the water system via a vent in the isolated part of the water system, before then closing the vent and detecting the pressures within the re-isolated part of the water system at that sensor at various intervals for a period of time long enough to obtain a second sequence of pressure readings.

The various intervals may be fixed intervals or variable intervals. Generally they are predetermined. Either way the intervals will be known or are recorded so that the pressures detected can be recorded against the time when they were taken. With the pressure and time data arising from this method, it becomes possible to extrapolate one or both sequences, one or both towards the other to allow an approximation of two pressures, these comprising a spike-corrected, pre-water-release pressure P2and a spike-corrected post-water-release pressure P3, ideally taken at a fixed time point corresponding to time t within the extrapolated data. It is thus after a first pressure reading P0was taken (P0can also be taken from the extrapolated data, it thus too being spike-corrected, if need be—from the first sequence of pressure readings).

With this data, the present invention can also seek to approximate an amount of water leaking from the system during time t (VL). The method then can further comprise:calculating an approximate leaked water loss VLby using the following equation:
VL=VR*P2(P0−P1)/(P0(P1−P2)).

As before, here the pressure readings are absolute pressures. Where they are gauge pressures, the formula may be substituted with the following:
VL=VR*(P2 gauge+PAtmospheric)*(P0−P1)/((P0 gauge+PAtmospheric)*(P1−P2)).

The method can also make a conclusion as to whether the leak is in need of investigation—if VLis greater than a predetermined value larger than 0, it is determined that there is a probable water leak to investigate.

Preferably each sequence of pressure readings comprises at least 4 pressure readings, and more preferably at least 10 pressure readings.

Preferably the period of time t is a period of time exceeding 20 seconds.

As with the first aspect, it is preferred that this method is carried out on a pressurised water system—i.e. with a pressure in excess of the pressure provided by the head of water above the sensor.

The extrapolation may be by fitting a straight line or curve through the or each sequence of pressure readings. The best-fit curve or line thus gives a smoothed or spike-corrected data set from which extrapolation is more readily achievable.

The line or curve enables a gradient or decay rate to be defined numerically. Commonly a leak results is a substantially linear gradient, if time t is between 5 minutes and an hour.

Variations of the above are as follows:1. Rather than fitting a gradient or decay rate to the pressure readings before a fixed volume of fluid is released, one could release the fluid and then continue measuring pressure readings after the volume of fluid is released, and fit a gradient or decay rate to these readings instead. This approach could be used to give the leak rate at the lower, post-release system pressure.

The leak rate might then be multiplied by a factor (e.g. pre-release pressure/post-release pressure) to estimate the pre-release leak rate.2. One could observe and record the drop in pressure during time tin the system due to a potential leak from a starting pressure P0, through to a final pressure P1, with as many intermediate readings as desired, but then re-pressurise the system to at or a little above the initial pressure P0, before releasing the water and either:a. Cause a fixed or measured volume of fluid/water to be released and continue with one of the processes described above;b. Cause fluid/water to be released from the system, but stop releasing fluid/water when the pressure is at or still above P1. By then measuring the volume of fluid you have released to achieve that pressure drop, you have an approximation of the amount of water leaked from the system in the first period t. Comparing this then to the time the system took to drop to the pressure it is now at due to the leak alone, a leak rate can be estimated. For example, if the system took 5 minutes to drop from 3.0 Bar to 2.9 Bar in the first run, and, after being re-pressurised to 3.0 Bar, releasing 20 ml of fluid caused a similar drop to 2.9 Bar, the leak rate could be estimated at 20 ml/5 mins=4 ml/min.3. A version of 2) above, but where the steps are carried out instead in the opposite order, and thus first one causes a fixed or measured volume of fluid to be released from the system, recording the pre- and post-release pressures, before then re-pressurising the system to at, or a little above the pre-release pressure and then recording how long it takes for the pressure to fall from the pre-release to the post-release pressure without water being released. All things being equal, the system will have lost the same volume of water through the leak as in the intentional water release, and thus the leak rate can be approximated.4. Another version but where an allowance is made for the fact that the release of fluid will not be instantaneous; this means that fluid will also be being released from the leak point at the same time as the release from the vent point, thus affecting the pressure readings.

Regarding version 4, according to the present invention it is preferred that the method involves extrapolating forward a gradient or fitted curve of the pressure profile recorded before fluid released to give an estimated pre-release pressure at the time the post-release pressure is recorded and thus an instantaneous pressure difference.

It is preferred alternatively that the method comprises extrapolating the gradient or fitted curve of the pressure profile recorded after fluid is released to give an estimated post-release pressure at the time the pre-release pressure was recorded and thus an instantaneous pressure difference.

Another correction can be to compare the time taken to drop from P0to P1due to the effects of the leak alone (tleak) to the time taken when fluid was being released (trelease), so that calculated leak rate can be corrected as:
Measured fluid released/(tleak−trelease)

To exemplify this, say that the process of releasing 20 ml of fluid took 30 seconds, while the initial leak from P0to P1took 5 mins. Then, throughout that 30 second period (0.5 minutes), the system was also leaking naturally, hence the total volume of fluid lost to cause the P0→P1pressure drop was actually 20 ml+leak rate/min*0.5, rather than just the 20 ml measured. Hence:
5*leak rate=20+0.5*leak rate
4.5*leak rate=20,
leak rate=20/4.5=4.44 ml/min.

It should also be noted that the leak rate calculated is an estimated average of the leak rate for the period when the system is observed—a period during which it is depressurising not least due to the presence of the leak. Since leak rate is proportional to gauge pressure, it is possible to determine the leak rate of the system at another desired pressure by taking the calculated leak rate, dividing by the average pressure over the observation period, and then multiplying by the desired pressure.

If multiple pressure readings have been taken during the depressurisation period, this can be further refined: Since discharge rate is proportional to gauge pressure, calculated total discharge volume will be proportional to the area under the depressurisation line or curve. This area could be calculated by integrating the derived line of best fit, or by summing the areas of the finite trapezoidal elements that will be described by each two successive pressure readings that were taken during the depressurisation period and the time period between them. Total discharge can then be calculated for any other pressure profile and time period (even if the pressure does not remain constant for this time period), by dividing the area under this new pressure profile with the area already calculated, and then multiplying by the known discharge rate.

Determining the Volume Lost Between Any Two Pressure Readings

Some of the above assumes that the measured release of water/fluid takes place either directly before an observed period of depressurisation, or that the pressure in the system is reset so that both the release and the observed depressurisation occur at similar pressures. Obviously it may not always be desired or possible to take the one reading directly after the other, or to re-pressurise the system between the two runs. This therefore raises the question, for a fixed system, with a suspected leak, whether, if we can measure the volume of fluid lost between two pressure readings, can we calculate how much fluid will be lost between any two other pressure readings?

To solve this the present inventors considered the following:

If discharging a volume of fluid V1from a system causes the absolute system pressure to fall from P11to P12and at a separate time, the pressure in the system is observed to fall from P21to P22, what volume of fluid ‘V2’ has been discharged to cause this separate (P21to P22pressure drop?

It is known that the absolute pressure of a system is inversely proportional to the volume of air trapped in it, so we can say that

P=k/V, where ‘k’ is a constant.

We assume that the volume of air present in the system at pressure P11is an unknown, called Vair1.

We thus can start with P11=k/Vair1and P12=k/(Vair1+V1)
ThusVair=k/P11
ThusP12=k/(kP11+V1),
Thusk*P12/P11+P12*V1=k
Thus (1−P12/P11)k=P12*V1
Thusk=P12*V1/(1−P12/P11)

Provided no air is allowed to enter or leave the system, ‘k’ will remain constant.

Looking then at the second pressure drop, with Vair2being the volume of air in the system when it is at pressure P21. It is again an unknown, but it will differ from Vair1:

As before we can start with P21=k/Vair2and P22=k/(Vair2+V2)
ThusVair2=k/P21,
ThusP22=k/(k/P21+V2)
ThusP22*k/P21+P22*V2=k
ThusP22*V22=k(1−P22/P21)
ThusV2=(1-P22/P21)*k/P22

Where, as previously defined k=P12*V1/(P12/P11)

Therefore, V2=P21/P22*V1/(1−P12/P11)*(1−P22/P21)

Which, multiplying through, comes to:
V2=V1*(P11*P12)/(P21*P22)*(P21−P22)/(P11−P12).

If instead using gauge pressures, rather than absolute pressures, then the equivalent equation will be:
V2=V1*((P11+Patm)*(P12+Patm))/P21+Patm)*(P22+Patm))*(P21−P22)/(P11−P12).

Where Patmis the atmospheric pressure.

Therefore, according to another aspect of the present invention there is provided a method for testing whether there is a leak in at least a part of a water system, comprising:closing all known water usage taps within the part of the water system to be tested;closing at least one stop cock or valve of the water system to isolate the part of the water system from its replacement water source (or sources), and any external replacement pressure source (or sources); and thena) detecting a first pressure P21within the isolated part of the water system, waiting a period of time t and then detecting a second pressure P22within the isolated part of the water system; andb) detecting a pre-release pressure P11within the isolated part of the water system, releasing a volume of water V1from the isolated part of the water system via a vent in the isolated part of the water system, before then closing the vent and detecting a post-release pressure P12within the re-isolated part of the water system;the method further comprising:
calculating an approximate leaked water loss V2by using the following equation:
V2=V1*(P11*P12)/(P21*P22)*(P21−P22)/(P11−P12).

Here the pressure readings are absolute pressures. Where they are gauge pressures, the formula may be substituted with the following:
V2=V1*P11+Patm)*(P12+Patm))/((P21+Patm)*(P22+Patm))*(P21−P22)/(P11−P12).

The leak rate can then be calculated by dividing V2 by time t, or with the correction described above for one or more of the previous aspects.

The above method, as before, can be used in either order (i.e. getting the two readings P21and P22could occur before or after the P11, P12, V1set of readings). Likewise, corrections for errors, as described above, can be used with this method. For example, allowances can be made for the system leaking at the same time as discharging a measurable volume of fluid. Ideally this might be done by carrying out the discharge of V1quickly, while taking a far longer amount of time between measuring points P21and P22—ideally a time-factor of more than 10, so that the leaked volume between P11and P12is small relative to the measured discharge, or by adopting a more elaborate methodology as described below:

When plotting the pressures (y axis) over time (x axis), a total discharge volume is proportional to the area under the pressure curve. Hence, where the total discharge volume is V1, the volume to be estimated is V2, the recorded discharge volume is VR, the area under the P11to P12pressure profile is area A1(seeFIG. 13for an example), the area under the P21to P22pressure profile is A2(again seeFIG. 13for an example), and a discharge constant is ‘C’, we can start with the following two formulas:
V1=VR+A1×CandV2=A2×C

Then, taking the earlier equation for V2:
V2=V1*((P11+Patm)*(P12+Patm))/((P21+Patm)*(P22+Patm))*(P21−P22)/(P11−P12)
and by temporarily referring to the term“((P11+Patm)*(P12+Patm))/((P21+Patm)*(P22+Patm))*(P21−P22)/(P11−P12)”
as ‘B’.

We can say that V2=V1*B.

Hence A2*C=(A1*C+VR)*B

Therefore C (A2−A1*B)=VR*B

Thus C=VR*B/(A2−A1*B)

And C=VR(A2/B−A1)

Therefore, for any given pressure profile, the present invention allows an improved estimation of the total fluid discharge that occurs over that profile by using the equation:
C×area under the profile
where C is (A2/B−A1) and
Bis ((P11+Patm)*(P12+Patm))/((P21+Patm)*(P22−Patm))*(P21−P22)/(P11−P12).

All of the previous workings monitor the pressure drop of a system due to a suspected leak and compare this to the pressure drop caused by the release of an additional, finite, measured volume of water. Furthermore, any additional leakage that occurs while the measured volume of water is discharged is either made sufficiently small that it can be discounted for the purpose of the estimation—for example by discharging the released volume of water relatively quickly compared to the time the leak is monitored, or is allowed for with additional calculations.

The present invention, however, considers another methodology, where a known additional leak in the system is used, whereby it becomes possible to compare the profile of the system pressure both before and after the additional intentional leak is set. According to this aspect of the present invention there is provided a method for testing whether there is a leak in at least a part of a water system comprising:closing all known water usage taps within the part of the water system to be tested;closing at least one stop cock or valve of the water system to isolate the part of the water system from its replacement water source (or sources), and any external replacement pressure source (or sources); and thena) taking several recordings of the system pressure dropping due to a suspected leak to give a set of suspected leak recordings, andb) setting an intentional leak in the system and taking several recordings of the system pressure dropping due to the intentional leak in addition to the suspected leak to give a set of intentional leak recordings;and comparing the two sets of recordings from steps a) and b).

Preferably the rate of the intentional leak is determined, either with a flow meter or by collecting it in a container for measuring its volume for a given time period shorter than the time the intentional leak is tested for.

Preferably the intentional leak recordings of step b) occur after the suspected leak recordings of step a).

Preferably no pressure reset is provided between sets of recordings, although as with earlier aspects, that is also possible.

The method may comprise fitting lines of best fit, or curves, to both sets of recordings and considering how much faster the pressure drops in the intentional leak recordings compared to the suspected leak recordings.

By using straight lines of the form y=a*x+b (or P=a*t+b), it is possible to compare the ‘a’ values for the two lines.

By using exponential decay curves of the form P=A exp{circumflex over ( )}(−lambda*t), it is possible to compare the lambdas.

It is also possible to extrapolate the curves, as in previous aspects, to account for set-up changes between not intentionally releasing water and releasing water intentionally (or vice versa).

It is also possible to extrapolate the lines or curves—a process that is particularly useful for more complex curves to allow the angles of both lines to the time axis, or the pressure drops, for both curves to be compared from the same time-point on the graph—usually from where the known leak is set as it is the easiest to measure.FIG. 14illustrates this approach. The ratio of intentional leak angle (or drop) “Δ2” to the suspected leak angle (or drop) “α1” will be the same as the known leak (VR+ the unknown leak VLdivided by the unknown leak VL. In other words:
Δ2/Δ1=(VR+VL)/VL

VLcan thus be calculated.

According to another aspect of the present invention there is provided a method for testing for a leak in a part of a vented water system that has a header tank:closing all known water usage taps within the part of the water system to be tested and isolating that part of the water system from its header tank such that an overflow pipe above the normal water line provides the only installed vent for the part of the water system to be tested;attaching one end of a u-tube manometer32to the overflow pipe, such that the liquid of the manometer seals the overflow pipe, the other end of the manometer then being open to the environment; andobserving whether the liquid in the manometer moves, movement suggesting the presence of a leak.

Preferably the liquid in the manometer is water.

The u-tube manometer can be a length of silicon or rubber tube part-filled with a little water.

Preferably the overflow pipe is for feeding over-pressurised hot water from a hot water cylinder back into the header tank for re-use.

Preferably the part of the water system is isolated from its header tank by a valve below the header tank, or by a bung in the bottom of the header tank.

Preferably, upon detecting the suggestion of a leak, the method comprises the step of measuring the rate of vertical movement v of the liquid in the manometer, the method then determining a leak rate as v*A, where A is the cross sectional area of the manometer.

Preferably the water systems are in a building. Typically the building will be a house, an apartment, an office, a warehouse or a factory.

According to a further aspect of the present invention there is provided a method for estimating a position or height of a leak within at least a part of a water system, the method comprising the use of two pressure sensors and a pump, wherein one of the two pressure sensors is located towards a top of the part of the water system being tested and the other pressure sensor is located towards a bottom of the part of the water system being tested, the pump being for enabling maintenance of a volume of air above the water level within the water system at a pressure greater than atmospheric to make the water in the water system pressurised, the method comprising:closing all known water usage taps within the part of the water system to be tested;isolating the part of the water system (50) from its replacement water source;checking the pressures on the sensors and elevating the pressure of the volume of air if needed to pressurise the water system; anddetermining the difference between the pressures sensed by two pressure sensors to determine a head of the water within the system, the head representing the height of the water above the second sensor;intermittently venting water out of the water system and measuring the pressures sensed by the two pressure sensors once the vents are closed to allow a subsequent head to be calculated; andre-ascertaining the differences between the pressures to calculate the new head;wherein if the detected pressures start to drop faster than normal whilst the system is isolated after one such intermittent or periodic venting of a volume of water, the location of a leak has been identified as at or just above the top of the water level, the height thereof being represented by the head just calculated.

The head is representative of the height above the lower sensor as the head is the pressure dictated by gravity. To calculate the height above the second sensor, the head in kPa should be divided by a gravity constant—usually about 10, or 9.81 m/s2, depending upon the altitude, or ambient pressure, to give a distance in meters.

In a vented water system, the above method may also use a pressure buffer, a pressure release valve or an inflatable device such as a balloon, connected to the volume of air, that can burst or open should the pressure in the volume of air be excessive—this prevents bursting of the pipe joints or pipe connections in that system, which joints or connections may be less resistant to bursting than those found in a normally mains pressurised water system. It also provides a second benefit—a reservoir of higher pressure air. This helps to ensure that the leak continues to occur even when head height is very near the leak height (whereby the head alone might otherwise no longer be able to drive the leak).

Preferably this method is used to schematically map a building's plumbing system. For this purpose the head is monitored as well. If the head remains constant for a sequence of water releases, the method will establish that the water system at that head comprises horizontal pipework. However, if the head drops during a sequence of water releases, then the method establishes that through that range of heads the water system comprises vertical pipework.

Preferably the vented water is vented as units of water. Preferably the units are fixed or measured volumes of water. The unit may instead be an approximated volume, determined by a timed duration of release.

With the information regarding the volume of water—approximated or measured, the method can then also approximate the cross sectional area of the vertical pipework at a given head by dividing the approximated or measured volume of water vented in a particular sequence by the change of head height measured. From this, as pipes tend to have a constant diameter, and given that pipes also tend to have standardised diameters, the number of pipes can be estimated.

Furthermore the method can approximate the length of horizontal pipes located in a horizontal stretch by dividing the approximated or measured volume of water vented by the expected cross-sectional area of the pipework. As pipes tend to be standardised, likely cross sectional areas can be used. Furthermore, visible pipework within the building can allow more reasoned conclusions to be drawn regarding the type of pipe that might be present, and thus their individual cross sectional areas.

The method can also monitor the head between each venting of a volume of water, in particular by looking for a drop in head when no water is being vented from the system. If after the initial release of water, the head is still slowly dropping, the water level is above the leak, so the testing should continue. However, if the head instead stops falling, the leak can be concluded to be in the horizontal section.

Throughout the method, it is preferred that if the measured pressure—e.g. at the top sensor, drops below a set minimum, the pump be used to pump more air in at the top as the pressure in the section being tested needs to exceed the static head pressure.

Similarly, if the pressure rises above a set maximum, e.g. due to excessive use of the pump, the pump or a pressure release valve should be allowed to let air out of the water system to avoid bursting joints of the water system, or to avoid causing other leaks to appear. The balloon, when fitted, can also provide such protection.

The present invention also provides an automated method for mapping at least a part of a water system, the method comprising the use of two pressure sensors and a pump, wherein an upper of the two pressure sensors is located towards a top of the part of the water system being tested and a lower of the two pressure sensors is located towards a bottom of the part of the water system being tested, the pump being for enabling maintenance of a volume of air above the water level within the water system at a pressure greater than atmospheric to make the water in the water system pressurised, the method comprising:closing all known water usage taps within the part of the water system to be tested;isolating the part of the water system (50) from its replacement water source;checking the pressures on the sensors and elevating the pressure of the volume of air if needed to pressurise the water system; anddetermining the difference between the pressures sensed by two pressure sensors to determine a head of the water within the system, the head representing the height of the water above the lower sensor;intermittently venting water out of the water system and measuring the pressures sensed by the two pressure sensors once the vents are closed to allow a subsequent head to be calculated; andre-ascertaining the differences between the pressures to calculate the new head;wherein if the head remains constant for a sequence of water releases, the method will establish that the water system at that head comprises horizontal pipework, and if the head drops during a sequence of water releases, then the method establishes that through that range of heads the water system comprises vertical pipework.

Preferably the method continues releasing water and measuring pressures until the head is measured to be zero.

As with the previous method, preferably the vented water is vented as units of water. Preferably the units are fixed or measured volumes of water. The unit may instead be an approximated volume, determined by a timed duration of release.

With the information regarding the volume of water—approximated or measured, the method can then also approximate the cross sectional area of the vertical pipework at a given head by dividing the approximated or measured volume of water vented in a particular sequence by the change of head height measured. From this, as pipes tend to have a constant diameter, and given that pipes also tend to have standardised diameters, the number of pipes can be estimated.

Furthermore the method can approximate the length of horizontal pipes located in a horizontal stretch by dividing the approximated or measured volume of water vented by the expected cross-sectional area of the pipework. As pipes tend to be standardised, likely cross sectional areas can be used. Furthermore, visible pipework within the building can allow more reasoned conclusions to be drawn regarding the type of pipe that might be present, and thus their individual cross sectional areas.

Throughout the method, it is preferred that if the measured pressure—e.g. at the top sensor, drops below a set minimum, the pump be used to pump more air in at the top as the pressure in the section being tested needs to exceed air pressure.

Similarly, if the pressure rises above a set maximum, e.g. due to excessive use of the pump, the pump or a pressure release valve should be allowed to let air out of the water system to avoid bursting joints of the water system, or to avoid causing other leaks to appear. The balloon, when fitted, can also provide such protection.

The present invention also provides a system for carrying out any one or more of the above methods.

The present invention also provides a pressure sensor module comprising a pressure sensor and a venting tap, the module further comprising a threaded cap—preferably sized to fit a washing machine attachment point, and tubing to connect the pressure sensor and venting tap with a water system of a building through the cap. Although reference is made to a washing machine attachment point, whereby the thread is a female thread, other standard attachment points might be used, such as valve attachments of a domestic tap, whereby the threaded cap would be a male fitting for fitting into that valve attachment point.

Preferably the sensor module also comprises a transmitter to transmit pressure readings taken by the sensor external of the module, and/or water volume indicators.

Preferably the transmissions are wireless transmissions.

The venting tap may be controlled by an actuator that is driven by a processor or computer.

The pressure sensor module may also comprise a receiver for receiving external pressure sensor readings transmitted from a separate pressure sensor—e.g. one at a top of a water system being tested, with the pressure sensor module being located at the bottom of the water system being tested.

Preferably the transmitter and receiver, the actuator and a control board therefor, the pressure sensor, the venting tap and the tubing, or flow channels, with the threaded cap for attaching to a washing machine attachment point, are assembled into an integrated assembly for sale as a single unit either alone, or in a kit comprising also a sensor and pump assembly for an upper end of a part of a water system to be tested or mapped therewith.

Preferably the sensor and pump assembly is also an integrated unit, with a receiver and transmitter, with a control board for the pump.

The kit may additionally comprise an app or program for a computer, tablet or smartphone such that the system can be monitored or controlled on the computer, tablet or smart phone.

A system comprising the sensor module as defined above, and the separate pressure sensor, both connected to a water system to be tested or mapped is also provided. The pressure sensors, or transmitters attached thereto, may transmit pressure information to a control or system processor for displaying results on a screen. The control or system processor may also send signals to a control board for an actuator of the venting tap, for automating the pressure sensing and water releasing process during a test or mapping process, such as those described above.

Alternatively or additionally the receiver may be for receiving control signals for selectively triggering the venting tap to release water from a connected water system when in use.

