6.20.345 Water pipe testing and disinfecting.
(1) Pressure Testing. All pipelines shall be pressure tested and disinfected prior to acceptance of work. A fire hydrant meter shall be required and procured from the district for all water utilized for flushing pipelines. All pumps, gauges, plugs, saddles, corporation stops, miscellaneous hose and piping, and measuring equipment necessary for performing the test shall be furnished, installed and operated by the developer. The developer shall provide an oil-filled pressure gauge with a range of zero to 300 psi.
In all instances, the contractor shall utilize a Washington State approved double check valve type backflow prevention assembly to protect the potable water supply while filling, flushing, and disinfecting the particular water main. The double check valve assembly shall have been tested within the last 30 days by a Washington State-certified BAT whenever used to connect to the water system, both prior to and during the project. The contractor shall provide a test certificate to the district.
The pipeline shall be backfilled sufficiently to prevent movement of the pipe under pressure. All thrust blocks shall be in place and time allowed for the concrete to cure before testing. Where permanent blocking is not required by the district, the developer shall furnish and install temporary blocking.
As soon as pipe is secured against movement under pressure, it may be filled with water. Satisfactory performance of air valves shall be checked while the line is filling. A temporary air vent will be required if the fill point is higher than the line being filled.
The developer shall pre-flush all water mains after water has remained in the main for 24 hours and before pressure testing the main unless otherwise approved by the district.
After the pipe is filled with water and all air expelled, it shall be charged by a pump to a hydrostatic test pressure of 250 psi, measured at the high point on the pipeline and this pressure shall be maintained for a period of not less than 30 minutes to ensure the integrity of the thrust and anchor blocks. All tests shall be made with the hydrant auxiliary gate valves open and pressure against the hydrant valve. Hydrostatic tests shall be performed on every complete section of water main between two valves, and each valve shall withstand the same test pressure as the pipe with no pressure active in the section of pipe beyond the closed valve.
Feed for the pump shall be drawn from a clean container wherein the actual amount of makeup water utilized can be measured periodically during the test period.
A separate 200 psi pressure test for 60 minutes will be required after all water services are cut to grade with angle stops or setters installed in the meter boxes.
In addition to the hydrostatic pressure test, a leakage test shall be conducted on the pipeline. The leakage test shall be conducted at 200 psi for a period of not less than 60 minutes. The allowable leakage rate per 1,000 feet of each size pipeline is as follows:
|
Pipe Size |
Allowable Leakage Gal. per Hour per 1,000 Ft. @ 200 psi |
|
4" |
0.21 |
|
6" |
0.32 |
|
8" |
0.42 |
|
10" |
0.53 |
|
12" |
0.63 |
|
16" |
0.85 |
Defective materials or workmanship discovered as a result of the tests shall be replaced by the developer at their expense. Whenever it is necessary to replace defective material or correct the workmanship, the tests shall be rerun at the developer’s expense until a satisfactory test is obtained.
(2) Disinfection. Before pipelines are placed in service, the water mains and appurtenances shall be disinfected in accordance with AWWA C651 and in conformance with the requirements of the State of Washington Department of Health Services.
In the process of chlorinating newly laid water pipe, all valves, fire hydrants and other district designated appurtenances shall be operated while the pipeline is filled with the chlorinating agent.
Chlorine shall be applied in the following manner to secure a concentration in the pipe of at least 50 ppm is maintained for a period of 24 hours:
(a) Injection of a sodium hypochlorite solution through a corporation cock at beginning of section after pipe has been filled, and with water exhausting at the end of section at a rate controlled to produce the desired chlorine concentration.
(b) The use of dry chlorinated lime for achieving disinfection is not allowed.
(c) The district shall provide the sodium hypochlorite solution for disinfection purposes. No other source of disinfection shall be allowed.
The developer shall be responsible for flushing all water mains prior to water samples being taken by the district. The water mains shall be flushed at a rate to provide a minimum two and one-half feet per second velocity in the main. Water mains shall be flushed until system achieves less than one ppm chlorine residual level.
In all disinfection processes, the developer shall take particular care in flushing and discharging the chlorinated water from the mains to ensure that the flushed and chlorinated water does no physical or environmental damage to property, streams, storm sewers or any waterways. Flushing water must be disposed of in accordance with Washington State Department of Ecology standards. Flushing water shall require dechlorination to prevent damage to the affected environment, particularly aquatic and fish life of receiving streams. Discharge of chlorinated flush water to the sanitary sewer system is prohibited, except with district approval.
District water quality staff shall designate sampling locations and obtain all disinfection process samples in accordance with AWWA requirements for testing purposes.
After the pipeline has been flushed and the system residual chlorine concentration has been obtained throughout the section of line, the water in the line shall again be left standing for a period of 24 hours. Following this, a water sample will be collected and tested. The line shall not be placed in service or connected to an existing main until a satisfactory bacteriological report has been received.
If disinfection of mains by the above methods proves unsatisfactory and the lab report indicates any type of bacteria count, then the developer shall rechlorinate using other methods in accordance with AWWA C651, approved by the district.
Only district representatives will be allowed to operate existing and new tie-in valves. The developer’s personnel are expressly forbidden to operate any valve on any section of line which has been accepted by the district.
(3) Early Water System Use. After the water system is substantially complete and when the use of the water system is requested by the developer for fire protection or other water uses prior to final project completion, the district may approve the charging of water mains for early fire protection or water use subject to the following conditions:
(a) Pressure test completed;
(b) System has been flushed;
(c) Results from purity test have been received and are satisfactory;
(d) All mainline is installed such to provide adequate flows;
(e) All valves and all hydrants are operational;
(f) All meter setters and boxes are installed and tested.
If the developer requests this option and meets the above conditions, the district may activate the water system. At this time, a copy of the final water availability certificate will be sent to the appropriate jurisdiction and fire marshal. [Res. 835 § 1 (Exh. 1), 2022; Res. 735 § 1, 2017. Formerly 6.20.340.]