Disinfection of Pipes FAQs
Q: Why do we disinfect pipes?
A: In order to safeguard water quality and public health it is generally a requirement that all private service pipes that are to be connected to the public water system are pressure tested and disinfected before the service is connected to the mains and commissioned.
Q: What part of the service pipe is private?
A: The part of the pipe between the boundary of the street, usually the property boundary, and the property itself. It is the responsibility of the owner of the property to maintain this pipe, although many water companies will offer to repair and sometimes replace this pipe if it is leaking.
Q: What part of the service pipe is maintained by the Water Company?
A: The pipe work between the water main and the edge of the street, usually the boundary of the property. It is sometimes called the communication pipe.
Q: What do you do to disinfect a water service?
A: The pipe is cleared of all debris by flushing before the pipe is disinfected. Chlorinated foam swabs may be used to clear particularly heavy sediments from the pipe.
The pipe is then dosed with a sufficient concentration of free chlorine which is left in contact with the pipe work for at least an hour before being tested. If the sample has retained enough free chlorine at the end of the disinfection process the pipe has passed the test and the highly chlorinated water is flushed to waste. For environmental reasons the waste water is de-chlorinated before it enters a drain or a water-course. The pipe is then capped pending connection and samples taken of the water for the bacteriological test.
The connection is usually made within 7 days of the disinfection process and may be flushed again to keep the pipe clean. If the pipe is left for more than 14 days it is usual to re-chlorinate and re-sample the pipe.
Q: Why use chlorine?
A: Chlorine is approved for the disinfection process by the Drinking Water Inspectorate (DWI). If some other disinfectant is specified then that must be a DWI approved product and the manufacturer's guidance regarding usage is followed.
Q: What is a bacteriological test?
A: This is the test conducted on a sample of water. It is usually analysed for the total number of coliform organisms present per 100ml, the total Escherichia coliform (e.coli) per 100ml at 22C and the 48 hour plate count at 37C. The 48 hour plate count is also known as the total viable count (TVC).
