8.1.9 Unvented storage systems
Unvented storage systems and discharge pipework shall be in accordance with relevant regulations. Be securely fixed and any discharge pipes terminate in a safe visible position. Issues to be taken take into account include:
- product certification
- discharge pipework
- low level discharge
- high level discharge
- discharge pipe material.
8.1.9.1 Product certification#
Unvented hot water storage systems should be:
- assessed in accordance with Technical Requirement R3, or meet the requirements of BS EN 12897 and be the subject of third-party certification, (applies to both the assembled system and components)
- installed by competent installers.
8.1.9.2 Unvented storage system discharge pipework#
Unvented storage discharge pipe work should:
- terminate in a safe and visible position
- have the tundish as close to the storage system as possible in a visible position
- not be connected to other waste connections
- not terminate inside garages
- be sized appropriately in line with national standards
- be adequately supported
- be installed with a fall to outside in line with the manufacturer’s recommendations.
8.1.9.3 Low level discharge#
Low level discharge should be:
- into a gully below the grating but above the water level. See figure 16
- onto the ground (drive, path or garden area) the pipe should discharge downwards and be no more than 100mm above ground level. The discharge should be protected against the discharge pipe being touched with fingers or hand before it has hit the ground. This is normally achieved by installing a cage over the discharge pipe. See figure 17.
Figure 16: Low level unvented discharge – trapped gully
Figure 17: Low level unvented discharge – path or garden area
8.1.9.4 High level discharge#
High level discharge is only acceptable when:
- it terminates onto a flat or pitched roof capable of withstanding water at high temperature
- the termination is 3m away from plastic guttering
- terminating into a metal hopper head and downpipe which in turn terminates safely at low level. Also see 8.1.9.3.
8.1.9.5 Discharge pipework material#
The normal material for discharge pipework is metal.
When thermoplastic pipes or fittings or similar equipment is used compliance with R3 is required. They should have a satisfactory assessment by an appropriate independent technical approvals’ authority accepted by NHBC.
Waterless traps and waste pipes should comply with the marking requirements of BS 7291-1 “Thermoplastic pipes and fittings for hot and cold water for domestic purposes”. See figure 18.
Last updated: 2nd January 2024