Internal services

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8.1.3Water 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:

  1. suitability of materials and components
  2. adequate supply
  3. durability
  4. protection from the cold.

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’.

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).


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.

Protection from the cold

To reduce the risk of freezing, water services should be located in the warm envelope of the home. 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), cisterns and vent pipes (particular care is needed around bends and junctions, especially near openings to the outside air, such as eaves)
  • as specified in the design (but not beneath a cold water tank)
  • on each side of raised tanks in unheated roof spaces
  • in accordance with BS 6700 or BS EN 806 and BS 8558.

Table 1: Minimum insulation thickness to delay freezing inside domestic premises for cold water systems

The conditions assumed for the table are:

  • air temperature -6°C
  • water temperature +7°C
  • ice formation 50%.

Table 2: Examples of insulating materials:

Thermal conductivity W/(mK)Material
Less than 0.020Rigid phenolic foam.
0.020-0.025Polyisocyanurate foam and rigid polyurethane foam.
0.025-0.030PVC foam.
0.030-0.035Expanded polystyrene, extruded polystyrene, cross-linked polyethlene foam, expanded nitrile rubber and improved polyethylene foam.
0.035-0.040Standard polyethylene foam, expanded synthetic rubber and cellular glass.

Where the floor is of suspended construction, the underfloor water service should be insulated as it passes through the ground and the ventilated space.