the invention lies in a treatment for maintaining uncontaminated water in closed dental unit water systems . many dental chairs used in dental offices are closed systems where the water for oral irrigation is self - contained . a dental unit water line is any one of several lines for conveying fluid from a reservoir to the dental instruments . the dental unit water system thus includes the reservoir , the dental instruments , the dental unit water lines , and any other components that come into contact with fluids from the reservoir during normal use . the reservoir is typically a plastic container designed to hold a predetermined amount of water . depending upon the design of the chair , the reservoir may require manual filling or may be filled by automatic connection to a water source , e . g ., tap water . a treatment system according to the invention contemplates use of a shock treatment and a maintenance treatment . typically , a dentist office will be closed for at least 24 hours out of each week . a shock treatment according to the invention is to be used after the last use of the dental chair prior to closing the office for at least 24 hours . the water reservoir in the chair is removed and emptied . an undiluted shock treatment formula is placed into the reservoir , and the reservoir is replaced in the dental chair . the shock solution germicidal in that it includes any chemical that it is strong enough to kill potentially harmful microbes . one optional shock treatment includes a pre - mixed 500 ml solution of shock treatment formula containing 440 ml of 5 ppm - 25 ppm silver colloid , 60 ml of 0 . 3 %- 30 % by weight hydrogen peroxide , a small amount of coloring , and a trace amount of sodium bicarbonate . in this solution , the coloring will comprise water , propylene glycol , fd & amp ; c red # 40 , and fd & amp ; c red # 3 . the target yield of active ingredients in the resulting shock treatment formula is 17 . 6 ppm silver and 3 . 15 % by weight hydrogen peroxide . a limitation of the premixed solution is that the silver and hydrogen peroxide tend to break down over time . for product stability , it has been found that a shock treatment comprising one container of 4 oz . of 15 ppm silver colloid and a separate container of 4 oz . of 6 % by weight hydrogen peroxide yields 7 . 5 ppm silver and 3 % hydrogen peroxide when mixed prior to use . the undiluted shock treatment formula is placed in the reservoir and directed from the reservoir through each water line attached to the dental chair for 20 - 30 seconds or until the coloration of the shock treatment formula is seen exiting the line . the shock treatment formula is allowed to remain in the system throughout the period in which the dental office is closed , typically a weekend . an acceptable range of ingredients for an effective shock solution is 0 . 3 %- 30 % by weight hydrogen peroxide and a minimum of 0 ppm silver colloid . prior to returning the dental chair to active use , each water line is flushed with shock treatment formula from the reservoir for about 20 - 30 seconds in order to detach any biofilm that may have accumulated inside the lines and to help prevent clogging of the dental instruments . thereafter , the reservoir is removed from the dental chair , and any remaining shock treatment formula in the reservoir is discarded . a maintenance treatment solution is then prepared and placed into the reservoir . the maintenance solution will include chemicals that inhibit the growth or reintroduction of harmful microbes , but remain safe for human consumption , perhaps in an undiluted state , but preferably diluted . a preferred maintenance treatment solution is formed by diluting one part maintenance treatment formula into thirty - two parts distilled water . a typical undiluted 125 ml solution of maintenance treatment formula contains 100 ml of 8 ppm - 25 ppm silver colloid , 25 ml of 0 . 0 %- 30 % by weight hydrogen peroxide , a small amount of coloring , and a trace amount of sodium bicarbonate . preferably , the coloring will comprise water , propylene glycol , and fd & amp ; c blue # 1 . the target yield for the maintenance treatment solution is 0 . 5 ppm silver and 0 . 1641 percent hydrogen peroxide . an acceptable range of ingredients for an effective maintenance solution is 5 - 25 ppm silver colloid and a maximum of 30 % by weight hydrogen peroxide . a preferred maintenance treatment solution comprises 4 oz . of 15 ppm silver colloid with no hydrogen peroxide , which when diluted in distilled water , yields a solution with 0 . 5 ppm silver and 0 % hydrogen peroxide . it has been found that the presence or absence of hydrogen peroxide in the diluted maintenance treatment formula makes no appreciable difference in effectiveness . a benefit of having no hydrogen peroxide in solution is that the undiluted maintenance treatment formula will have a longer shelf life . the prepared maintenance treatment solution is placed in the reservoir , and the reservoir reattached to the dental chair . each dental unit water line is then flushed with the maintenance treatment solution until the coloration of the shock treatment formula is replaced by the coloration of the maintenance treatment solution . the dental unit water lines will now be ready for patient use . it will be understood that the maintenance treatment solution is fully capable of consumption by patients with no harmful effects . for ease in preparing the maintenance treatment solution , a predetermined amount of maintenance treatment formula can be supplied in a package or container , and a visual indicium , such as a fill line , can be placed on the reservoir at an appropriate level . the appropriate level would be predetermined such that when the predetermined amount of maintenance treatment formula is placed in the reservoir , the proper dilution will automatically occur when distilled water is added to the reservoir until the solution reaches the fill line . it is preferable that only distilled water be used in order to minimize interference with the anti - microbial properties of the maintenance treatment solution . testing has revealed the effectiveness and acceptable ranges of active ingredients . a dental unit water line treatment system according to the invention was tested in six dental chairs at different strength levels . prior to use , baseline samples were taken from all six dental chairs in a dentist ″ s office , and sent to a lab where cultures were incubated and counted at 48 hours and 72 hours . the results are seen in table 1 : [ t1 ] room 48 hr cfu 72 hr cfu 1 200 450 2 1300 2350 3 * tntc tntc 4 1400 1900 5 ( control ) 1550 2700 6 tntc tntc * tntc means “ too numerous to count .” a shock treatment solution was prepared and used in each chair according to the following concentrations in table 2 : [ t2 ] room ag + h 2 o 2 1 10 ppm . 3 % 2 10 ppm . 3 % 3 10 ppm . 3 % 4 10 ppm . 3 % 5 ( control ) 0 0 6 10 ppm . 3 % samples were then taken from all six dental chairs after use of the shock treatment formula with the following results in table 3 : [ t3 ] room 48 hr cfu 72 hr cfu 1 & lt ; 1 . 0 & lt ; 1 . 0 2 & lt ; 1 . 0 & lt ; 1 . 0 3 & lt ; 1 . 0 & lt ; 1 . 0 4 & lt ; 1 . 0 & lt ; 1 . 0 5 ( control ) tntc tntc 6 & lt ; 1 . 0 & lt ; 1 . 0 a maintenance formula was prepared and used in each dental chair according to the following concentrations in table 4 : [ t4 ] room ag + h 2 o 2 1 . 25 ppm 0 2 . 5 ppm 0 3 . 75 ppm 0 4 1 ppm 0 5 ( control ) 0 0 6 . 5 ppm . 03 % samples were then taken from all six dental chairs after two weeks ″ use of the maintenance formula solution with the following results seen in table 5 : [ t5 ] room 48 hr cfu 72 hr cfu 1 & lt ; 1 . 0 & lt ; 1 . 0 2 & lt ; 1 . 0 & lt ; 1 . 0 3 & lt ; 1 . 0 & lt ; 1 . 0 4 & lt ; 1 . 0 & lt ; 1 . 0 5 ( control ) tntc tntc 6 & lt ; 1 . 0 & lt ; 1 . 0 it can be seen that the present invention provided an effective solution to the problem of contaminants in dental unit water lines . reasonable variations and modifications can readily be made without departing from the scope of the invention .