The guidelines for commissioning new water mains and services highlight essential steps to ensure a safe, compliant network. Below is an overview of the full water main commissioning process:
Routine Flushing
Regular flushing is necessary to prevent stagnant water during construction, and helps maintain water quality before commissioning.
Swabbing
Mains (63mm and above) require swabbing to eliminate debris. Chlorinated swabs are used if contamination is suspected, and swabbing continues until clear water is achieved. This ensures the network is clean before pressure testing and chlorination.
Pressure Testing
Pressure tests start at ambient levels. If not connected within three months, testing must be redone. This confirms the integrity of the water main and ensures compliance with commissioning requirements.
Chlorination
Disinfection requires a chlorine concentration of 20 mg/L for at least 16 hours. Different requirements may apply for connections to incumbent networks.
If not connected within a month of chlorination, the pipe must be re-chlorinated. This step ensures the main is disinfected to industry standards.
Dechlorination
Chlorine levels are monitored before and after dechlorination with sodium bisulphate, ensuring levels are appropriate before proceeding. Water quality must be confirmed as safe before sampling.
Flushing
Mains must be flushed until visibly clear, with a minimum of two pipe volumes. Final flushing removes residual contaminants and prepares the main for sampling.
Sampling
Samples should be taken from the main and endpoints at least 16 hours after dechlorination, flushing, and charging. Only satisfactory sample results allow the water main to progress to connection.
Timescales
The commissioning process requires three days for completion. Sample results will be provided after an additional five working days.
Once satisfactory results are confirmed, the mains connection must be completed within a maximum of 14 calendar days from the date of sample collection; otherwise, new samples will need to be collected.
Other considerations:
Personnel
Workers must be part of an approved hygiene scheme, possess valid water hygiene training cards, and hold at least an NVQ Level 2 in Network Construction Operations.
Sampling staff must follow ISO/IEC 17025 training standards, as required for water quality compliance.
Fixtures and Fittings
Pipes and fittings should be stored off the ground with end caps to avoid contamination and kept clear of fuel oils, supporting safe and hygienic installation practices for adoptable water networks.