Who is responsible for arranging chlorine disinfection for mains?

Responsibility normally rests with the party controlling the project and commissioning the mains installation, but the contract should allocate each task clearly. The client or developer may hold the overall responsibility, while a principal contractor, main contractor or specialist mechanical contractor arranges the practical work. The disinfection itself should be planned and completed by a competent water hygiene contractor, with the required evidence passed to the project’s responsible person.

The correct allocation depends on the type of mains involved and the stage of the project:

• New development or building project: the developer or client usually specifies that the new installation must be disinfected and provides for the work within the project programme. The principal contractor may then appoint a suitable specialist and coordinate access, isolation, flushing and reinstatement.
• Alteration or extension: the organisation instructing the modification should ensure that the affected section is included in the disinfection plan. This may be the building owner, facilities operator, contractor or another party with control of the works.
• Private water main or internal distribution main: the owner or operator remains responsible for making sure the installation is suitable before it is brought into service, even where the physical work is delegated to a contractor.
• Connection or adoption involving a water undertaker: the project team must check the undertaker’s requirements and agree the format of the commissioning evidence. The undertaker may have approval or acceptance requirements, but this does not remove the project’s need to arrange the work and retain suitable records.

The person arranging the treatment should not select a contractor solely because it can dose chlorine. Competence includes understanding the pipework design, identifying all sections requiring treatment, selecting an appropriate method, controlling chemical risks, carrying out representative sampling and interpreting the results. The contractor should also be able to explain any failed or inconclusive result and recommend the necessary corrective action.

Responsibility should be confirmed before construction or modification begins. A written scope should identify:

• the pipework, branches, fittings and storage components included in the treatment;
• who will provide isolation, access, water, drainage and safe working conditions;
• which party will notify relevant stakeholders and coordinate with the water undertaker where applicable;
• the agreed disinfection procedure, sampling arrangements and acceptance criteria;
• who will review the results and authorise connection to the occupied or operational system; and
• who will retain the method statement, chemical information, completion records and laboratory results.

The principal contractor or project manager should coordinate the timing. Chlorination may need to take place after installation work is complete but before the mains is connected to the wider potable water system or placed into service. Other trades should not be permitted to alter treated pipework without assessing whether further disinfection is required. If the system is opened, extended or contaminated after treatment, the original certificate may no longer demonstrate that the final installation is suitable.

After handover, responsibility changes from commissioning to operational control. The owner or operator of the premises should know which pipework was treated, retain the commissioning information and include the installation within its wider water safety arrangements. This is particularly important where the mains supplies healthcare, residential, commercial or industrial premises, or where it forms part of a larger building water system.

Blue Fish Water Management Ltd can advise clients, developers and contractors on the division of responsibilities, prepare or review the relevant documentation, and arrange specialist mains disinfection and water testing. Its support is available to projects nationally, helping the commissioning party establish what must be completed before the mains is accepted for use.