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Commissioning plumbing systems

We provide general guidance and clarification, in accordance with the Water Supply Byelaws 2002, on the requirements for commissioning, flushing and maintaining new plumbing systems that are used in households to supply water for domestic purposes. We also provide guidance on ways to maintain the quality of water supply.

Regardless of the materials used for plumbing systems, inadequate commissioning, flushing and maintenance can affect the quality of the water supply. Building debris or pipe trimmings (swarf) left in newly installed pipework can block or damage fittings. Debris left in poorly flushed pipework can encourage the growth of bacteria.

Excess soldering flux left inside copper pipes may lead to corrosion, causing the amount of copper in the water to exceed the permitted amount for drinking water. This could have undesirable health effects and, in extreme circumstances, result in 'blue water'. The causes of blue water corrosion are complex and poorly understood. 

We have a duty to enforce the Water Supply Byelaws 2002. We will undertake inspection of a proportion of new and existing installations to check that the Byelaws are being met. Where breaches of the Byelaws are found, we will issue an enforcement notice to require compliance within a given timescale. It is a criminal offence to breach the Byelaws; offenders may face disconnection of their supply and prosecution.

It is a requirement that an Authorised Person be used for the installation work, as this provides the client with a measure of protection under the regulations. A list of Authorised Persons can be obtained from us.

The Byelaws state that:

  1. The whole installation should be appropriately pressure tested. Details are given in The Water Regulations Advisory Scheme's Water Regulations Guide (Section 4: Guidance clauses G12.1 – 12.3), which requires a pressure test to 1.5 times the maximum operating pressure for the installation or relevant part.
  2. Every new water service pipe, cistern, distributing pipe, hot water cylinder or other appliance and any extension or modification to such a service shall be thoroughly flushed with drinking water before being put into use.
  3. Under certain circumstances the system should be disinfected before being put into use.

It is essential that each length of pipe within the system is flushed to remove any debris including excess flux that may have collected in the pipework during installation. The following guidance is given as to the procedure which should be employed.

  1. Open all terminal fittings to produce as high a flow of water as possible.
  2. Allow water to run until visually clear.
  3. Continue to allow water to run for a further 2 minutes.
  4. Confirm that the water is visually clear by filling an appropriate clean container such as a clear plastic bottle or washbasin with at least 1 litre of water.
  5. If the water appears cloudy, discoloured or contains any debris then repeat the flushing process. If after repeated flushing the water is not visually clear then contact us.

Disinfection where underground services are installed, renovated or modified is normally only required for pipes above 50 mm internal diameter, although this must be confirmed with us. Where disinfection of incoming pipework to buildings is required, the service pipe between the boundary of the property and its entry into the premises should be disinfected by arrangement with us.

Disinfection of newly installed internal plumbing systems is not normally required for private dwellings occupied by a single family. It is usually sufficient for the system only to be pressure tested and flushed out. For other types of new installations, and for major extensions or alterations to existing systems in properties in multiple occupation (for example flats, offices, hotels etc), disinfection of the internal plumbing systems is required before use.

In all types of premises, where there is any suspicion of contamination of the plumbing installation by sewage, ground water or the entry into pipes by insects or vermin, disinfection must be carried out.

Details on methods for disinfection of plumbing are given in BS 6700:1997 Specification for design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages.

Stagnation of water in installed pipework can occur in:

  • newly constructed properties which are awaiting occupancy
  • show homes on new developments where not all parts of the system are in normal use
  • en-suite bathrooms that are not regularly used
  • infrequently used taps, for example in cloakrooms
  • redundant pipework following modification to the plumbing installation

Water which is left to stagnate in pipework can lead to a general deterioration in water quality which for both plastic and metallic pipes can give rise to taste and odour problems. It may also be involved in causing 'blue water' corrosion.

Stagnation is suspected as one of the causes of 'blue water' corrosion in newly installed copper pipework. This happens when the natural protective layer, which normally forms quickly on new copper pipework, fails to do so and the pipe starts to corrode. This releases copper into the water and can lead to a characteristic blue cloudy appearance of water drawn from the outlet. To minimise water quality problems caused by stagnation it is recommended that:

  • where newly completed copper pipework is unlikely to be used within a few days after flushing or pressure testing, it should be drained down to prevent it being left with water standing in it
  • if this is impracticable, the water system should be flushed once or twice per week to prevent the water stagnating. It is also sensible to do this where existing copper pipework is unlikely to be used on a regular basis
  • in newly-occupied premises, each day for a fortnight occupants should ensure that the taps used for drinking purposes are run briefly until the water becomes noticeably cooler to clear standing water from the pipes serving them

After the successful commissioning of any new plumbing installation there are steps the occupier should take to ensure that drinking water quality is not affected by the way the system is used.

Water from hot water taps should not be used for drinking or cooking purposes.

Water from storage cisterns should not be used for drinking unless the cisterns are designed and maintained to ensure the water remains wholesome.

It is strongly advised only to use the cold-water tap in the kitchen for all drinking and cooking purposes. Water that has stood in pipework overnight or longer can pick up abnormal tastes and odours and minute traces of metallic substances. In such cases, before water is used for drinking or cooking purposes, the taps should be run for a few seconds until the water becomes noticeably cooler. This water can be used for other purposes, for example, washing, watering plants etc.

The Water Supply Byelaws 2002

The Byelaws Inspector can be contacted by telephoning (01624) 687687.

The Water Regulations Approval Scheme
Unit 13
Willow Road
Pen y Fan Industrial Estate
Crumlin
Gwent
NP11 4EG

Tel: (01495) 244666

Email: info@wrasapprovals.co.uk

Website: www.wrasapprovals.co.uk (information and guidance notes are available)

The Water Regulations Guidance outlines the regulations along with the Water Industry's recommendations for complying with the regulations. It is published by and available from Water Regs UK. 

The Water Product Approvals Directory lists products which have been tested and approved by the water suppliers for their compliance with the regulations.

Further information and advice can be found in the following publications:

Dial Before You Dig

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