referring now to fig1 , network pipe 2 is 900 mm in diameter and branch pipe 4 brings water to the 1200 - mm diameter tank 6 through a butterfly valve 8 past a flow meter 10 . referring now to fig2 and 3 , the regulator valve 12 is bolted to the end of the branch pipe 4 and discharges into the tank . the valve body stem 14 is a t - shaped pipe of 320 mm diameter , the body being 510 mm long and the valve body stem 14 terminating in a connector ring 16 with bolt holes 18 for connection to the end of the branch pipe 4 . both the body 20 and the valve member 22 ( fig4 ) are made of stainless steel . water enters the regulator valve 12 via the valve body stem 14 and discharges through the open ends of the body 20 . the flow through the valve is controlled by the valve member 22 , which is a sleeve of the same length as the valve body , namely 510 mm . referring now to fig2 , the circumferential gap 24 is bridged by a trio of bearing strips 26 made of a slippery polymer and attached to the edge of the valve member by stainless steel fasteners ( not shown ). the strips are spaced at 120 degrees , enabling the member to rotate in the body with minimum friction . referring now to fig4 , the crown of the valve member 22 has a cutout 28 with a straight edge 30 and tapered edges 32 extending over about 90 degrees of the circumference of the member . the cutout 28 lies in register with the connector ring 16 . the ends of the valve body 20 have pairs of slots 34 , 36 , 11 mm wide ( see fig2 and 5 ) extending 90 degrees around the quadrants facing the water below the valve body 20 . the slots 34 , 36 define the path of a pair of 10 - mm diameter stainless steel rods 38 that are a slide fit in the slots . the rods pass through bores 39 near the edge of the valve member and are bent at one end into a foot 40 ( fig2 ) that is secured to the valve member by a split pin 42 ( fig2 ). the foot 40 is housed in the thickness of the valve member 22 and the end of the pin 42 rides in the slot in the valve body . referring to fig2 , the opposite end of each rod has a bore that receives a shackle 44 for connecting the arm to float chain 46 . the chain is about 600 mm long and runs through the shackle and is attached to itself . the chains each capture a spherical molded plastic float 48 . the floats are balanced by pivoted counterweights 50 . the chain 46 adjusts to suit the water level required . this allows for almost any water level required to be accommodated without affecting the functionality of the valve . in use , the pipework is installed and the valve is suspended above or within the operational range of water levels in the tank . the floats lie on the surface of the water and the counterweights rotate the valve body to the open position . as the land dries and the tank empties the floats lie on the tank floor . when the operator opens the butterfly valve 8 , the meter begins to measure flow . the operator selects a suitable flow rate and the container allows inflow to feed the outflow pipes . the tank level rises and equilibrium is established . if the incoming flow fluctuates , the valve restores the equilibrium by rotating . it is not the purpose of the valve to halt flow . that is the task of the butterfly valve 8 . the valve ensures a constant head of water in the tank , whereby the irrigation proceeds in an orderly manner despite the fluctuations in the network . a head of 3 m to 5 m is usual in such networks , but this may spike to 10 m . in a second embodiment , fig5 a and 6 show valve body stem 14 is divided by a pair of square frame plates 52 , 54 . plate 52 is attached to the valve body 20 . plate 54 is attached to the part of the stem with the connector ring 16 . the gap 62 between the parallel plates 52 , 54 is bridged by pairs of gate guides 56 , 58 attached to the upright side edges of frame plates 52 , 54 . for both guides 56 , 58 , the gate gap 62 extends the full length of the guide . the gate itself is a modified m - shape made of steel sheet that is wider than the gate guides spacing and has two legs 64 , 66 joined by an upper part 68 with a convex leading edge 70 . the legs have slots 72 , 74 for reception of the pivoting connections 76 , 78 ( fig7 ) of float arms 38 . in the open position shown in fig5 , the gate rises clear of the frame plates 52 , 54 . in the closed position shown in fig9 , the leading edge 70 meets the circular perimeter of valve body stem portion 14 and the part 68 registers with the frame plates 52 , 54 . the float arms 38 are fixed to the sleeve 22 to ensure that the floats exert the same uplift force as in the previous embodiment . the pivoting connections each have a central self - lubricating bush through which the float arm is free to slide in order to accommodate the linear rise and fall of the gate . the projection of the rods through the legs 64 , 66 is seen in fig6 and 9 . the counterweights &# 39 ; mass is increased to adjust for the weight of the gate . the float arms lie in an intermediate position when the tank is both filling with network inflow and emptying into the irrigation pipes . the cutout 28 of sleeve 22 registers with the valve body stem 14 and , from this position , the floats quickly react to any increase in head . if the head persists , the floats press the gate into the closed position . as the tank drains , the floats descend . if the head has diminished , the gate may not reopen . if the tank drains further , the gate may reopen . in a third embodiment , fig1 shows an irrigation channel 3 m to 4 m wide and 2 m deep that is fed by a steel pipe that brings pumped water from a bulk source such as a dam . the shape of the channel is as shown in fig1 and the pipe is submerged so that the floats can exert flow control on the incoming water . referring now to fig8 and 9 , the float - activated stop valve is connected to the external delivery conduit by ring flange 16 . stem 14 is 300 mm in diameter and 700 mm long . the rise and fall gate straddles an incision ( not shown ) in the upper half of valve body stem 14 . the steel gate guides 56 , 58 are separated by gap 62 and welded to the outer surface of the valve body stem 14 . gate gap 62 extends the full length of the guides . the gate itself ( see fig1 ) is a modified m - shape , made of stainless steel that is wider than the width of the gate guides and has two legs 64 , 66 joined by an upper part 68 with a convex leading edge 70 . the legs have slots 72 , 74 for the reception of the pivoting connections 76 , 78 of float arms or rods 38 . the guides 56 , 58 have pairs of slots 77 adjacent gate gap 62 in order to support the screws of pairs of vertical self - lubricating polymer strips 79 . the slots 77 allow accurate adjustment of gap 62 size leading to smooth motion of the gate . upper part 68 supports a semi - circular collar 80 , 25 mm wide , which overlies the incision when the gate is closed . in the closed position , the convex leading edge 70 contacts the circular wall of the stem . the 22 . 5 degree rotary motion of the float arms 38 is made possible by the horizontal transverse pivots 82 welded to the outside wall of the valve body stem 14 . the counterweights and floats work in the same way as described in related australian patent application serial no . 2013902805 . the water flow passes between the parallel float arms . referring now to fig1 , the leading edge 70 closes the duct by descending to contact the lower cylindrical wall of the valve body stem 14 . the semi - circular collar 80 then rests on the upper part of the same wall . it is to be understood that the word “ comprising ” as used throughout the specification is to be interpreted in its inclusive form , i . e ., use of the word “ comprising ” does not exclude the addition of other elements . it is to be understood that various modifications of and / or additions to the disclosure can be made without departing from the basic nature hereof . these modifications and / or additions are , therefore , considered to fall within the scope of the invention .