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8.1.3 Water services and supply
Water services shall be based on the pressures and flow rates supplied from the incoming main. Components shall be selected and installed to ensure satisfactory service for the life of the system, with suitable precautions taken against corrosion and damage. Issues to be taken into account include:
- suitability of materials and components
- adequate supply
- durability
- protection from the cold
- wholesome water
- water efficiency.
8.1.3.1 Suitability of materials and components#
Relevant standards for materials and components used in domestic water systems include:
| BS EN 806 | ‘Specifications for installations inside buildings conveying water for human consumption’ |
| BS EN 12897 | ‘Water supply. Specification for indirectly heated unvented (closed) storage water heaters’ |
| BS EN 1057 | ‘Copper and copper alloys. Seamless, round copper tubes for water and gas in sanitary and heating applications’ |
| BS 1566 | ‘Copper indirect cylinders for domestic purposes’ |
| BS 3198 | ‘Specification for copper hot water storage combination units for domestic purpose’. |
| BS 7291 | ‘Thermoplastics pipes and fitting systems for hot and cold water for domestic purposes and heating installations in buildings’ |
| BS 8558 | 'Guide to the design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages. Complementary guidance to BS EN 806’ |
8.1.3.2 Adequate supply#
The design and installation of the water services supply should:
- be in accordance with Building Regulations, statutory requirements and the recommendations of the water supplier
- ensure drinking water is provided at the kitchen sink direct from the supply pipe or, where this is impracticable, from a storage cistern containing an adequate supply of drinking water
- be based on a minimum 1.5 bar dynamic pressure at the stop valve inside the home
- ensure a minimum 20L/min flow rate is available at the stop valve inside the home
- account for pressure and flow rate reductions (a wider supply pipe may be required inside the home)
- account for pressure fluctuations and surges, which may occur within the system and potentially damage fittings (surge arresters may be required)
- ensure that stop valves within the curtilage and outside the home are protected by a shaft or box
- ensure service pipes are a minimum of 750mm below the ground surface – where this is not possible, adequate precautions should be taken against frost and mechanical damage
- ensure that underground ducts are sealed at both ends to prevent the entry of fluids, vermin and insects
- be of materials which are safe and minimise the risk of corrosion
- be in accordance with the recommendations of the water supplier, including compatibility of the supply with the materials and fittings
- the water system should be capable of being drained (hot and cold services separately).
8.1.3.3 Durability#
The hot and cold-water service should be installed using corrosion resistant pipes and fittings.
In areas where pitting corrosion of copper cylinders occurs, it may be necessary to fit aluminium protector rods. These should be fitted during manufacture in accordance with the relevant British Standard. Sacrificial anodes should be installed where required by the water supplier.
8.1.3.4 Protection from the cold#
To reduce the risk of freezing, or condensation forming on the pipework, water services should be located in the warm envelope of the home. Where possible, water pipes should be below the main roof insulation.
Particular care is needed with cisterns, vent pipes, bends and junctions, especially near openings to the outside air, such as eaves.
Where they are located in unheated spaces, they should be insulated and not affected by cold. Insulation should be provided:
- around water services, including pipework (in accordance with Tables 1 and 2)
- as specified in the design (but not beneath a cold-water tank)
- on each side of raised tanks in unheated roof spaces
- even where it is below the main roof insulation. See figure 1, 2 & 3
- in accordance with BS EN 806 and BS 8558.
Figure 1: Protection from the cold - loft space
Figure 2: Protection from the cold - header tanks
Figure 3: Pipe insulation thickness
Table 1: Minimum insulation thickness to delay freezing inside domestic premises for cold water systems taken from BS 5422:2009 table 30. See figure 3
The conditions assumed for the table are:
- air temperature -6°C
- water temperature +7°C
- permitted ice formation 50%
- evaluation period 12 hours
- installation inside the building
- for practical reasons if the pipe and insulation diameter are too large to be applied in practice then insulation with a lower thermal conductivity should be used.
Table 2: Examples of insulating materials:
| Thermal conductivity W/(mK) | Material |
|---|---|
| Less than 0.020 | Rigid phenolic foam |
| 0.021 to 0.035 | Polyurethane foam |
| 0.040 to 0.055 | Corkboard |
| 0.055 to 0.07 | Exfoliated vermiculite (loose fill) |
Where the floor is of suspended construction, the underfloor water service should be insulated as it passes through the ground and the ventilated space. See figure 4.
8.1.3.5 Wholesome water#
There must be suitable installation for the provision of wholesome water to any place where drinking water is drawn off.
8.1.3.6 Water efficiency#
Water efficiency should be accounted for in any design to prevent waste and undue consumption.
Water efficiency can either be by a fittings approach or a water efficiency calculator or other approved method acceptable to NHBC.
Last updated: 8th February 2024