Advice and Guidance | Dwr Cymru Welsh Water
Dwr Cymru Welsh Water

Advice and Guidance

Poor plumbing may cause very serious problems, such as harm to health, and could lead to poor water quality.

Since 1999, the regulations have been in place. Before that, there was the water regulation byelaws (or ‘the byelaws’). Any plumbing systems or fittings installed after 1999 have to follow the regulations, anything installed before date falls under the byelaws that were in place at that time. 

Who is included in the regulations?

All customers who have drinking water from us, or need a drinking water supply, as well as any plumbers and installers involved, may need to know about the regulations.

Building owners and occupiers, developers, designers and architects, may also need to know about the regulations. Even customers who have their own private water supply (e.g. they get drinking water from their own well / borehole) may need to know, if they are also connected to, or are planning to become connected to, the drinking water we supply.

What is included in the regulations?

The regulations explain how to design, fit and look after plumbing systems and fittings. They have our safety in mind, and want to protect us against problems such as:

  • Contamination (e.g. nasty chemicals in drinking water);
  • Waste (e.g. plumbing systems that leak); and,
  • Misuse; undue consumption; and, erroneous measurements (e.g. water meters installed in the wrong places, or people illegally using the drinking water supply).

Protecting customers against contamination entering the drinking water supply is one of our biggest concerns. When visiting customers, we undertake a risk assessment, to help find the problems and work out how they can be fixed. This could be instances like stopping water returning back into pipework, by fitting non return valves, through to fitting air gaps.

There are 5 categories of contamination or chemicals in drinking water. The following table gives the ‘legal bit’, from Fluid Category 1 (e.g. clean safe drinking water) to 5 (e.g. water that could cause very serious harm). 

Fluid Category



Wholesome water supplied by a water undertaker and complying with the requirements made under section 67 of the Water Industry Act 1991 (a).


Water in fluid category 1 whose aesthetic quality is impaired owing to:

a)         A change in its temperature; or,
b)         The presence of substances or organisms causing a change in its taste, odour or appearance, including water in a hot water distribution system.


Fluid which represents a slight health hazard because of the concentration of substances of low toxicity, including any fluid which contains:

a)         Ethylene glycol, copper sulphate solution or similar chemical additives; or,
b)         Sodium hypochlorite (chloros and common disinfectants).


Fluid which represent a significant health hazard because of the concentration of toxic substances, including any fluid which contains:

a)         Chemical, carcinogenic substances or pesticides (including insecticides and herbicides); or,
b)         Environmental organisms of potential health significance.


Fluid representing a serious health hazard because of the concentration of pathogenic organisms, radioactive or very toxic substances, including any fluid which contains:

a)         Faecal material or other human waste;
b)         Butchery or other animal waste; or,
c)         Pathogens from any other source.


We, and other UK water companies, are members of the Water Regulation Advisory Scheme (WRAS), and use best practice to meet the regulations (see here). WRAS describe themselves as below:

The purpose of WRAS is to contribute to the protection of public health by preventing contamination of public water supplies and encouraging the efficient use of water by promoting and facilitating compliance with the Water Supply (Water Fittings) Regulations and Scottish Byelaws.


WRAS have regular meetings, events and workshops, and issue guidance to us on the regulations. They also undertake training and assessment for the approved plumbers (see ‘Approved Installers’ section).

Their website ( has lots of useful information about products / materials / fittings that WRAS approve for use in plumbing systems, and also the approved plumbers schemes (see ‘Approved Installers’ section). The website has a resource section with information and leaflets about how the water regulations fit in to things like your home, farming or agriculture, rainwater harvesting, caravan sites etc.

WRAS may be able to help you personally, and will answer your calls. If you would prefer all the information about the regulations in one place however, for a small cost you can buy WRAS’ water regulation guide from their website.

WRAS’ address is:

Unit 13, Willow Road,

Pen-y-fan Industrial Estate, Crumlin,

Gwent, NP11 4EG,

Telephone: +44 (0) 333 207 9030, or international +44 (0) 1495 244 666

The Water Regulations Team

Our water regulations team help customers follow the regulations, by contacting customers, arranging visits, and having our officers check the plumbing systems and fittings. Places that have more hazards such as chemicals on site e.g. hospitals, farms and sewage treatment works, are visited more regularly. When plumbing systems or fittings don’t comply with the regulations, depending on circumstances, they may need to be corrected by the customer, or the installer. The water regulations officer can give further information during their visit, such as about approved installers

Our customer enforcement policy can be found here. (You can find the Welsh version of our policy here.)

Other Useful Sources of Information

You may be interested in the drinking water section of our website, and the developer services section of the website

You can buy hard copies of the regulations from HMSO, at, or view it at the following links:

The Water Regulations Advisory Scheme (WRAS) website has very useful guidance about all things ‘regulation’, at

The Department of Environment Food and Rural Affairs (DEFRA) is also a good source of information about the regulations, some has been archived, but can be found here.