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020 4532 7773If you are managing a new build or a renovation project in London that involves a new mains water connection, chlorination is not optional. Thames Water requires that all new pipework is chlorinated, flushed and tested before a connection will be approved, and that a UKAS-certified chlorination certificate is issued upon completion.
For developers, project managers and contractors working to tight programme deadlines, understanding what the chlorination process involves and how to get it done efficiently can make a real difference to how smoothly the connection stage goes. Delays at this point can hold up the entire project, so knowing what is required and having a reliable specialist booked in advance is always the better approach.
This post sets out what mains chlorination involves, why it is required, and what to expect from the process.
New pipework, however well installed, is not sterile. During the construction process, pipework can be exposed to dust, debris and contamination from the surrounding environment. Even with careful site management, the inside of new pipes can harbour bacteria and other organic material that must be removed before the system is connected to the public water supply.
Chlorination is the process used to disinfect new pipework before it enters service. A chlorine solution is introduced into the system, left to dwell for a specified period, and then thoroughly flushed out. Water samples are taken and tested to confirm that the system is clean and that chlorine residuals are within the required limits before the certificate is issued.
Thames Water, like all water undertakers in the UK, requires this process to be completed and certified before they will approve a new connection to the mains. This is not simply a procedural requirement. It is a public health measure designed to ensure that new pipework does not introduce contamination into the wider distribution network.
The chlorination process for a new mains connection typically follows a set sequence. First, the pipework is filled with a chlorine solution at the required concentration. The solution is then left to dwell in the system for a minimum period, usually at least one hour for new installations, though this can vary depending on the size and complexity of the system.
During the dwell period, the concentration of chlorine in the solution is checked at various points in the system to confirm that an adequate level is being maintained throughout. Once the dwell period is complete, the system is flushed thoroughly with clean water until the residual chlorine levels fall within the acceptable range.
Water samples are then taken from the system and sent to a UKAS accredited laboratory for analysis. The laboratory tests the samples to confirm that the water meets the required bacteriological and chemical standards. Once the results come back satisfactory, the chlorination certificate can be issued.
At London Water Treatment, we provide the full process from start to finish, including the chlorination itself, the laboratory testing and the UKAS-certified certificate on completion. We understand that programme deadlines matter on construction projects, and we work to turn the process around as efficiently as possible. Find out more about our chlorination services in London.
The chlorination certificate issued at the end of the process is not simply a piece of paperwork. Thames Water requires that the certificate is produced by a company using a UKAS accredited laboratory for the water sample analysis. UKAS accreditation is the United Kingdom Accreditation Service's mark of technical competence, and it provides assurance that the laboratory results are accurate and reliable.
If a certificate is produced using a non-UKAS accredited laboratory, Thames Water may reject it and require the process to be repeated. That is a delay and an additional cost that no project manager wants to deal with, particularly at a late stage in the programme.
When you book a chlorination service with London Water Treatment, the sample analysis is carried out by a UKAS accredited laboratory as standard. The certificate we issue meets Thames Water's requirements and is accepted without issue.
Mains chlorination is not only required for new builds. Any project that involves significant work to the internal pipework, including the replacement of sections of the distribution system, the installation of new outlets or the extension of existing pipework, may require chlorination before the system is put back into service.
Where a renovation involves the cold water storage tank as well as the pipework, a tank clean and disinfection may be required alongside the chlorination. This is particularly relevant for older commercial properties in London where the tank may not have been inspected for some time and the renovation work provides a practical opportunity to address any water hygiene concerns.
If you are planning a refurbishment project and are not certain whether chlorination will be required, it is worth discussing the scope of the works with a water treatment specialist early in the project. Getting clarity on what is needed before work starts is considerably easier than trying to arrange it at short notice once the programme is already running.
For a straightforward residential or small commercial installation, the chlorination itself can typically be completed within a day. The limiting factor is usually the laboratory turnaround time for the water sample analysis, which is normally between one and three working days depending on the laboratory and the urgency of the request.
At London Water Treatment, we work to minimise the overall turnaround time as much as possible. Where a project is particularly time-sensitive, we can discuss options for expediting the process and will always be transparent about realistic timescales before the work begins.
If you are working to a tight deadline for a Thames Water connection, the most important thing is to book the chlorination service early enough that the certificate can be in hand before the connection date. Leaving it to the last minute is the most common cause of unnecessary delays on site.
If you have a new build, renovation or infrastructure project in London that requires mains chlorination and Thames Water certification, our team at London Water Treatment can help.
We provide chlorination services across London for residential and commercial projects of all sizes, from single dwellings to large multi-unit developments. All work is carried out by experienced engineers, sample analysis is done through a UKAS accredited laboratory, and certificates are issued promptly on completion.
To discuss your project requirements or to book a chlorination service, contact our team today. Call us on 020 4532 7773 or visit our chlorination services page for more details on what we cover.
