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6.3.78.1.10 Soil and waste systems internal
Soil and waste systems shall be in accordance with relevant Building Regulations and installed to ensure that effluent is removed without affecting health or creating unnecessary noise and smell. Items to be taken into account include:
- relevant standards
- air admittance valves
- sound insulation to soil and vent pipe (SVP)
- sanitary fittings
- waste disposal
- junctions.
Soil and waste systems should be:
- in accordance with the requirements of the water supplier
- adequately ventilated at the head of underground drains (this may be by a soil pipe or separate ventilation pipe)
- adequately ventilated at each branch
- arranged to ensure foul air from the drainage system cannot enter homes (eg ventilated to 900mm above openings when within 3m)
- fixed neatly and securely to provide the correct falls
- fitted to prevent the entry of vermin.
8.1.10.1 Relevant standards#
Relevant standards for domestic soil and waste systems include:
| BS EN 752 | Drain and sewer systems outside buildings |
| BS EN 12056‑1 | Gravity drainage systems inside buildings. General and performance requirements |
| BS EN 12056‑2 | Gravity drainage systems inside buildings. Sanitary pipework, layout and calculation |
| BS EN 12056‑3 | Gravity drainage systems inside buildings. Roof drainage, layout and calculation |
| BS EN 12056‑4 | Gravity drainage systems inside buildings. Wastewater lifting plants, layout and calculation |
| BS EN 12056‑5 | Gravity drainage systems inside buildings. Installation and testing, instructions for operation, maintenance and use |
8.1.10.2 Air admittance valves should#
Air admittance valves should:
- be used to allow air to enter the drainage system (but do not avoid the need to ventilate it adequately)
- comply with BS EN 12380 or be assessed in accordance with Technical Requirement R3. See figure 19
- not be positioned in areas which are liable to freezing
- have free movement of air around them which can be achieved by ventilation grilles, discreet gaps around the boxing or ventilation of the boxing into a ventilated roof void (the ventilation area should be 2500mm2 minimum unless otherwise specified by the manufacturer). See figure 20
- where positioned within the home, be accessible for maintenance.
8.1.10.3 Sound insulation to soil and vent pipes#
All sections of soil and vent pipe including those in bathrooms or ground floor stub stacks, should be soundproofed to limit the transmission of noise. See figure 19.
Where soil and vent pipes run horizontally through a floor void above or below a habitable room they should be:
- wrapped in at least 25mm of mineral wool (10kg/m3 min)
- adequately supported to avoid contact with the floor decking or ceiling.
Sound insulation should be provided to soil pipes passing through homes by:
- an encased boxing, using material (15kg/m2) and
- wrapping the pipe with a minimum 25mm of unfaced mineral wool (10kg/m3 min). The insulation should be continued through the thickness of each sound-insulating floor).
Soil and vent pipes which hold a satisfactory assessment by an appropriate independent technical approvals’ authority acceptable to NHBC, maybe acceptable where the requirements of the Building Regulations are achieved.
8.1.10.4 Sanitary fittings#
Sanitary fittings should be:
- installed with accessories, such as chains and plugs
- secured using non-ferrous or stainless steel screws or fixings appropriate to the weight of item being secured
- fitted without using excessive packing
- fitted to ensure WC lids and seats are stable when open.
8.1.10.5 Waste disposal#
Waste disposal units should be:
- provided with adequate support
- fitted with a tubular trap (not bottle or resealing)
- connected to the drainage system in accordance with the manufacturer’s recommendations.
8.1.10.6 Junctions#
The junctions of wall tiling with baths and showers should be made watertight using a flexible sealant to accommodate movement. The manufacturer’s instructions should be followed.
Last updated: 2nd January 2024