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SECTION 3 Schedule 2: Paragraphs 3, 4, 5, 6 and 7: Requirements for water fittings Every water fitting shall- be immune to or protected from corrosion by galvanic action or by any other process which is likely to result in contamination or waste of water; and be constructed of materials of such strength and thickness as to resist damage from any external load, vibration, stress or settlement, pressure surges, or temperature fluctuation to which it is likely to be subjected. Every water fitting shall- be watertight; be so constructed and installed as to- prevent ingress by contaminants, and inhibit damage by freezing or any other cause; be so installed as to minimise the risk of permeation by, or deterioration from contact with, any substance which may cause contamination; be adequately supported. Every water fitting shall be capable of withstanding an internal water pressure not less than 11/2 times the maximum pressure to which the fitting is designed to be subjected in operation. No water fitting shall be installed, connected or used which is likely to have a detrimental effect on the quality or pressure of water in a water main or other pipe of a water undertaker. (1) No water fitting shall be embedded in any wall or solid floor. (2) No fitting which is designed to be operated or maintained, whether manually or electronically, or which consists of a joint, shall be a concealed water fitting. (3) Any concealed water fitting or mechanical backflow prevention device, not being a terminal fitting, shall be made of gunmetal, or another material resistant to dezincification. (4) Any water fitting laid below ground level shall have a depth of cover sufficient to prevent water freezing in the fitting. (5) In this paragraph "concealed water fitting" means a water fitting which- is installed below ground; passes through or under any wall, footing or foundation; is enclosed in any chase or duct, or is in any other position which is inaccessible or renders access difficult.

Guidance

General

G3.1   Water fittings should be adequate for the purpose and satisfy the appropriate British Standard, or acceptable equivalent.

G3.2   Pipes of different metallic materials are not to be connected unless suitable precautions are taken to ensure that corrosion through galvanic action cannot take place.

G3.3   All water fittings including supply pipes, distributing pipes and discharge pipes connected to operational and safety devices in cold and hot water systems should be capable of withstanding temperatures to allow for malfunctions within the system and should comply with the requirements of BS 6700.

G3.4   The suitability and thickness of copper hot water storage vessels and other apparatus should not be determined exclusively on the basis of pressure considerations. A greater thickness of the walls of the vessel, together with the need or otherwise of protector rods or internal coating, should take into consideration the type of water supplied in the area and its possible effect in combination with other factors.

Watertightness of fittings

G4.1   Water fittings are to be watertight, suitable for the default pressures and temperatures likely to be encountered within the installation.

Protection against freezing

G4.2   All cold water fittings located within the building but outside the thermal envelope, or those outside the building should be protected against damage by freezing.

G4.3   If the frost protection provided is insufficient for exceptional freezing conditions, or the premises are left unoccupied or without adequate heating, damage and leakage can often be avoided by shutting off the water supply and draining the system before the onset of freezing.

G4.4   Where low temperatures persist insulation will only delay the onset of freezing. Its efficiency is dependant upon its thickness and thermal conductivity in relation to the size of pipe, the time of exposure, the location and possibly the wind-chill factor.

G4.5   In exceptional circumstances, and in those parts of the United Kingdom where very low temperatures are sustained during both day and night, unless the system is isolated and drained before the onset of freezing, additional measures may be required to ensure that freezing of water fittings does not occur. Other methods of preventing damage to water fittings that may be considered are the;

1. provision of froststats to activate the heating system when the air temperature drops to a preselected value; and,
2. provision of strategically placed thermostatically controlled shut-off and draining valves for isolating and draining sections of pipework.

G4.6   Thermal insulating materials should be of the closed cell type complying with BS 5422 and be installed in accordance with BS 5970.

G4.7   Some of the types of insulation materials relating to the thermal conductivities shown in Table 3.1 are as follows:

Less than 0.020 W/(m.K)	Rigid phenolic foam
0.020 to 0.025 W/(m.K)	Polisocyanurate foam and rigid polyurethane foam
0.025 to 0.030 W/(m.K)	PVC foam
0.030 to 0.035 W/(m.K)	Expanded polystyrene, extruded polystyrene, cross-linked polyethylene foam, expanded nitrile rubber and improved polyethylene foam
0.035 to 0.040 W/(m.K)	Standard polyethylene foam, expanded synthetic rubber and cellular glass.

G4.8   It is essential that:

1. there is no gap in the insulation at bends, valves, etc. as heat loss due to these conditions could freeze local pockets of the pipe system in less than one hour; and,
2. an external vapour barrier is provided and protected against mechanical or other damage; and,
3. where water pipes are located directly below ceiling or roof void insulation;
   1. the full calculated thickness; or,
   2. a minimum thickness of 9mm, high emissivity surfaced, closed cell insulation, whichever is the greater, is installed around the water pipe to prevent condensation, saturation and subsequent failure of the ceiling insulation.

G4.9   Hot water fittings outside the thermal envelope, where water is likely to be static for a period, should be protected against freezing. The thickness of insulation applied to hot water pipes for energy conservation purposes is usually of insufficient thickness to protect against low temperature conditions.

G4.10   Stop valves, servicing valves and drain taps should be labelled so that the parts of the system which they control can be determined for maintenance purposes; also for isolation and draining when buildings are unoccupied during cold weather.

G4.11   For the purpose of protection against freezing of pipes two conditions are assumed:

1.     Normal conditions

   In domestic accommodation, and in other types of premises where applicable, where habitable rooms are normally heated for up to 12 hours each day; water fittings in unheated rooms need to be protected against freezing, particularly overnight, even though they are within the envelope of the heated accommodation. For example, water fittings in cloakrooms, store rooms, utility rooms, in roof spaces but located below the ceiling insulation, etc.

   The recommended commercial thicknesses of insulation for minimum and practical protection against freezing in the unheated parts of normally occupied buildings when the heating is turned off in the remainder of the building, such as overnight, is shown in Table 3.1. Except where indicated otherwise, the insulation thicknesses shown under the respective thermal conductivity values are considered reasonable to provide a nominal minimum of 12 hours protection. An absence of more than 24 hours is not considered normal occupation.

2.     Extreme conditions

   Water fittings installed outside a building, or inside any building or part of a building which is unheated, or only marginally heated for less than 12 hours each day; or water fittings inside a building but located outside the thermal envelope. For example, water fittings located under suspended ground floors, above the level of ceiling insulation in a roof space, in a communal staircase or corridor in flats, domestic garages or other buildings, or externally above ground level.

   It is recommended that for water fittings in these locations the thickness of insulation should be substantially increased and the advice of insulation specialists or manufacturers be obtained. Guidance on design methods can be obtained from BS 5422.

   It should be noted that the principal criteria used in BS 5422 (water temperature, ambient temperature, time of exposure, percentage ice formation, thermal conductivity and thickness of insulation) cannot represent all circumstances or permutations, so that where it is necessary to avoid excessive ice formation it would be prudent to consult insulation suppliers or manufacturers.

G4.12   Self-regulating trace heating conforming to BS 6351, in conjunction with a nominal thickness of thermal insulation, is an acceptable method of protection against freezing.

G4.13   The thickness of insulation for the protection of cold water cisterns in roof spaces and other exposed locations should be calculated in accordance with BS EN 1057. Water fittings connecting to and from cold water cisterns are particularly vulnerable and all insulation should be closely sealed, except for the air vent to the cistern.

Plastics and permeable materials

G4.14   Water fittings should be installed to minimize any risk of contamination by permeation of fluids through the material or materials used.

G4.15   Water fittings that are made of a material which is susceptible to permeation by any fluid that causes, or is likely to cause, contamination of water passing through the fitting, should not be laid or installed in such a location, in relation to other services or contaminated ground, that permeation occurs.

G4.16   Water fittings made of plastics, or other material which are likely to be damaged by exposure to oil, petrol or any other contaminant, should not be laid in contaminated ground, or should be protected.

Fixing of water fittings

G4.17   Water fittings should be adequately protected against damage from any cause, including the environment through which they pass.

G4.18   Water fittings should be adequately supported, the spacing for support being dependent on the material of the pipes. Allowance should be made to accommodate any reasonable foreseeable movement, including thermal movement, in accordance with clause 3.1.7 of BS 6700.

Pressure requirements

G5.1   All water fittings should be capable of withstanding an internal water pressure of not less than 1.5 times the maximum operating pressure.

G5.2   In determining the maximum operating pressure to which the system is subjected, the increase in static pressure in the following instances should be taken into consideration:

1. the supply pipe during night periods when there may be little demand on the system; and,
2. in any water supply installation where pumps are installed.

Surge pressures

G5.3   The internal test pressure does not take into consideration any transient or surge pressures which may be generated within the system and the designer or installer should take the effect of any surge into consideration in determining the test pressure applied to an installation.

G5.4   Transient pressure increases or surge (water hammer) may be generated by the rapid closure of a valve; for example, float-operated valves, spherical valves or disc valves. When installed, attenuation devices or water hammer arresters may reduce the effects of surge.

Pumps or boosters

G6.1   Written approval should be obtained from the water undertaker before any pump or booster is connected to a supply pipe, unless the pump or booster is incapable of drawing more than 0.2 litres per second.

Pumped showers

G6.2   Showers, and other appliances, which are supplied with water through a pump located either upstream or downstream of the mixing valve, and capable of delivering more than 0.2 litres/second, may not be supplied with water direct from a supply pipe unless written approval has been obtained from the water supplier. (See Regulation 5).

G6.3   Irrespective of whether the water supply to a shower is pumped or the shower incorporates a pump, whether supplied with water from either a supply pipe or a distributing pipe, and is of a type specified by the regulator, consent to instal the shower should be obtained from the water undertaker. (See Regulation 5).

Location of water fitings

G7.1   Unless they are located in an internal wall which is not a solid wall, a chase or duct which may be readily exposed, or under a suspended floor which may, if necessary, be readily removed and replaced, or to which there is access, water fittings should not be:

1. located in the cavity of a cavity wall; or,
2. embedded in any wall or solid floor; or,
3. installed below a suspended or solid floor at ground level.

See Figure 3.1and 3.2 for typical details of acceptable arrangements.

[Note: Any notching or holes made within floor or roof joists should be within the limits shown in Building Regulations, Approved Document A, Section 1B6.]

G7.2   Pipes entering buildings at the approved depth should be passed through a duct and the ends of the duct sealed as shown in Figure 3.3 to prevent the ingress of gas or vermin into the building.

Concealed fittings

G7.3   A concealed pipe may be installed in a pipe sleeve or duct located under or within a solid floor provided that the pipe can be readily removed and replaced.

Dezincification resistant materials

G7.4   Water fittings are to be resistant to corrosion and, where specified, to dezincification.

G7.5   All concealed water fittings, except terminal fittings, (including those buried underground), together with backflow prevention devices, are required to be manufactured of gunmetal or other dezincification resistant materials.

G7.6   Dezincification resistant fittings should be of DRA quality, the depth of dezincification being not less than 200 microns in any direction. Each fitting should be marked with the symbol CR or DRA and should be tested in accordance with ISO 6509.

Water fittings laid underground

G7.7   Wherever practicable and except for pipes laid under a building, the vertical distance between the top of every water pipe installed below ground and the finished ground level should be:

1. not less than 750 mm; and,
2. not more than 1,350 mm.

G7.8   Where compliance with the minimum cover of 750 mm is impracticable, and with the written approval of the water undertaker, the water fittings should be installed as deep as is practicable below the finished ground level and be adequately protected against damage from freezing and from any other cause. For further information see Figure 3.4.

G7.9   Water fittings laid underground should be resistant to dezincification and be installed to accommodate any movement.

G7.10   Water fittings installed underground should not be jointed or connected to any other water fitting by adhesives.

Table 3.1: Recommended minimum commercial thicknesses of thermal insulation for copper water pipes of minimum wall thickness complying with BS EN 1057 in normal conditions of exposure.
External diameter of pipe	Thermal conductivity of insulation material at 00 C in W/(m.K)
	0.02	0.025	0.03	0.035	0.04
mm 15 22 28 35 42 and over	mm 20 (20) 15 (9) 15 (6) 15 (4) 15 (3)	mm 30 (30) 15 (12) 15 (8) 15 (6) 15 (5)	mm 25* (45) 19 (15) 13 (10) 9 (7) 9 (5)	mm 25* (70) 19 (19) 19 (12) 9 (8) 9 (5)	mm 32* (91) 25 (24) 22 (14) 13 (10) 9 (8)
Notes Except for 15 mm pipes with thermal conductivities of 0.030, 0.035 and 0.040 W/(m.K), shown with a *, which are limited to 50% ice formation after 9, 8 and 7 hours respectively, the above recommended commercially available minimum thicknesses of insulation should limit ice formation to under 50% after 12 hours for the remainder of the pipe sizes, when based on an air temperature of -60 C and a water temperature of +70 C. The minimum calculated insulation thicknesses for 12 hours protection under the above conditions are shown in the appropriate location in brackets. Commercial thicknesses of insulation with the higher thermal conductivities are generally limited to a minimum of 9 mm. Materials with a lower thermal conductivity, such as rigid phenolic foam, polisocyanurate foam and rigid polyurethane foam are installed by specialist firms and are usually limited to a minimum thickness of about 15 mm. Normal conditions to frost exposure are considered to be when water fittings are installed inside buildings within the thermal envelope, but within rooms or voids which are not heated for a minimum period of 12 hours each day for the whole of the winter period. Examples could include the following: Unheated cloakrooms, store rooms, utility rooms, etc. Below the ceiling insulation in a roof space

Figure 3.1: Location and accessibility of concealed water fittings in floors

Note: Any notching or holes made within floor or root joists should be within the limits shown in Building Regulations 1991 - Approved Document A, 1B6.

Figure 3.2: Location and accessibility of concealed water fittings in walls and behind baths

Figure 3.3: Details of pipes entries to buildings

Figure 3.4: Depths of pipes below ground

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Published 22 December 1999

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