If a premises has any form of mains water supply, then the water fittings regulations in England, Wales and Northern Ireland, byelaws in Scotland, apply.
These legal requirements play an important role in protecting public health and safeguarding water supplies. Their purpose includes preventing the contamination and waste of water supplied by a water undertaker once it has entered a customer’s plumbing system.
In addition to the restrictions on installation set out in regulation/byelaw 3 and requirements for water fittings specified in regulation/byelaw 4, schedule 2 includes a number of installation requirements, several of which are applicable when installing pipework.
When designing a compliant plumbing system a number of factors need to be considered, including but not limited to:
Avoiding the risk of contamination or damage resulting from the environment in which the system is to be installed or due to the design itself.
The required and attainable supply pressure and other operational parameters
User expectations and whether these are achievable
Suitability of water fittings for use
Providing appropriate, adequate backflow protection.
Water efficiency
Limiting waste.
Useful sources of information include BS EN 806 and BS 8558
To help prevent waste and contamination all pipe and fittings systems must be of an appropriate quality and standard and suitable for the circumstances in which they will be used.
Before installing a pipe and fittings system key considerations will include but are not limited to:
The compatibility of the pipe and fittings. For example, to ensure connections are watertight and configured to prevent galvanic action.
Whether the pipework is to be installed above or below ground
Where the pipework is to be installed. For example, in contaminated ground, in a duct and potentially exposed to construction materials and/or water vapour, somewhere exposed to sunlight or sources of heat.
What water temperatures and pressures the pipework will be exposed to. For example, hot or cold water only, heating systems, maximum operating pressure and thermal shock.
In the case of metallic water fittings, the possibility of corrosion due to galvanic action and dezincification.
Useful sources of information include BS EN 806 and BS 8558
Please note:
All water fittings should be resistant to corrosion. In the case of mechanical backflow prevention devices and metallic fittings which are not going to be readily accessible, in addition to being corrosion resistant these should be manufactured from materials which are not susceptible to dezincification. For example, gunmetal or CR brass.
As non-metallic pipe and fittings can be affected by sunlight and/or allow ingress of light, which is known to promote the growth of algae, consideration should be given to whether protective measures to exclude light are necessary.
Adhesive joints are not acceptable below ground.
The supply pipe to a building should enter at a depth of 750 mm.
Pipework passing through walls and laid at depths of less than 750 mm, including any inside the building should be ducted. This is to prevent damage and facilitate ease of replacement, the internal surface of the ducting should be smooth bore i.e. any ridging to be external only.
The pipework should be sealed using a method acceptable to the local water undertaker. This is to prevent ingress of gases and vermin. It should also be adequately insulated. Where pipework is installed below a suspended floor if there is an air vent the pipework should be ducted and insulated to the finished floor level.
The acceptability of the methods of protection for pipework is dependent on a number of location specific factors, such as the type and size of water fitting, the likely water supply and air temperatures as well as demand flow. Manufacturers usually provide information about the appropriate thickness and thermal conductivity in their technical specifications. BS EN ISO 12241 and BS 5422 are another source of useful information.
When installed in accordance with the manufacturer’s instructions insulation may delay but not prevent freezing. Examples of pipework entering a building at and below street level are given below.
Firstly, the pipe and fittings, including method of connection, should be suitable for below ground use and the environment in which they are to be installed. Joints should be kept to a minimum. Water fittings which are susceptible to permeation by hydrocarbons should not be laid in ground near installation storing or ground contaminated with petrol or oil unless protected.
Pipework should be laid at a depth of not less than 750 mm (to limit the effect of freezing and mechanical damage) and no greater than 1350 mm deep. They should be embedded in nonabrasive materials. Where this cannot be achieved in all circumstances the consent of the local water undertakers must be obtained via notification.
Where the local water undertaker consents to pipework being laid at less than 750 mm it should be installed as deep as possible below ground level and protected against warming, freezing and mechanical damage (for example due to ground movement).
Pipework should not be installed above ground level is not permitted without the agreement of the local water undertaker.
Pipework should never be installed in a contaminated environment such as a sewer or cesspool.
Non-metallic (plastic) plumbing fittings are at risk of permeation by diesel or heating fuel, pesticides, insecticides and similar organic substances or fluids, so should never be installed where they could come into direct contact, including contact with soil contaminated with them.
Where this is unavoidable contact the local water undertaker for advice.
Joints on concealed pipework are likely to lose their integrity over time and therefore should only be considered where unavoidable.
To prevent waste there needs to be provision to access any joints or water fittings which require maintenance, such as backflow prevention devices, valves which control the flow and any other operational fitting.
Water fittings considered to be concealed include those:
Buried in the ground
Installed below or embedded in floors
Installed in or behind wall finishes
Water fittings considered not to be concealed include those:
Installed below ground but not buried, such as in a chamber or basement room
Installed below floors or in walls which can be readily accessed
All domestic hot and cold water system pipework concealed within walls should:
Be installed with a minimum number of joints. This is because joints are prone to a loss of integrity over time and therefore should only be considered where unavoidable.
Be installed in a chase/duct or void. Wrapping pipework in insulation is not an acceptable method of ducting or passing through a chimney is not an acceptable method of ducting.
With the agreement of the local water undertaker pipework may be installed alongside other services in a shared duct. An example of what may be considered as acceptable is shown below.
Be appropriately clipped to avoid water hammer and other stresses which would affect the integrity of the installation.
Be insulated with a suitable gap maintained between the cold water, hot water and any other heat source to prevent heat transfer or loss.
Not be embedded or come into contact with other materials such as plaster or cement.
Be accessible to enable inspection and replacement. Further information about accessibility can be found in BS 8558.
Below are images illustrating domestic hot and cold water systems concealed in a wall and a soil pipe duct.
Regulations & Byelaws which apply include but are not limited to:
Relevant guidance includes but is not limited to:
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