Thames Water Chlorination

Under the Water Supply (water fittings) Regulations 1999 (SI 1999, 1148), you will be required to disinfect your underground pipe work prior to connection.

The disinfection must be carried out to 'BS6700'. This is to ensure there is no detriment to public health.

For further details and clarification, please refer to section G13.1 of the Guidance Notes to S1 1999, 1148 and clause 3.1.10 of BS6700.

New supplies should be swabbed, flushed, filled with chlorinated water not less than 50mg/l and allowed to stand for 1 hour, following which the chlorinated water should be flushed out, the pipe refilled, and a sample taken. The pipework must be disinfected with a 'hypochlorite solution'.

The following must be submitted to our office prior to the connection being made:

• A disinfection certificate
• A method statement of the disinfection process carried out
• The sample results

The 'certificate' must indicate the name of the company performing the disinfection, date of disinfection, confirmation that the pipe has been swabbed and flushed prior to disinfection, a 'hypochlorite' solution has been used, the chlorine level of the source water, the chlorine level after dosing, the contact time, the chlorine level after contact, and the chlorine level after flushing. It must also detail the onsite test for appearance, odour and taste.


The certificate must clearly state that the disinfection has been carried out in accordance with BS6700. The 'method statement' must indicate the details of the disinfection carried out, the diameter and length of pipe disinfected, the source of the water used, the sample location point, and a diagram. The 'sample results' must include E-coli, total coliforms, turbidity, and plate counts taken at both 22°C and 37°C. The post flush chlorine level must also be confirmed by laboratory analysis. The sample results must be from a 'UKAS' accredited laboratory. It is the customer's responsibility to ensure that the designated disinfection company is aware of our requirements. If this procedure is not met we have a right to refuse the final connection, and the pipework must be re-disinfected to meet our requirements.

Please note that we cannot begin the connection process until we have received these documents complete with all information.

The disinfection certificate, the bacteriological sample results, and the method statement should be sent to 112 Broad Street Coventry CV6 5AZ or faxed to 0207 713 3888.