Sanitary Appliances
This domain tests whether you can choose, fit and connect sanitary appliances so that they flush, drain and remain hygienic, and whether you know the access requirements that apply.
Appliances and connections
WC pans to EN 997 are commonly 6/4 L dual flush, with a trap seal of at least 50 mm. Washbasins take a 32 mm waste, baths and sinks 40 mm, and a WC a 110 mm branch. Keep the trap close to the appliance outlet and make it accessible for cleaning.
Traps and seals
The trap holds a water seal against sewer gas. Seals are lost by self-siphonage, induced siphonage, back pressure, evaporation, capillarity and compression. Deep-seal traps and correct venting solve most of these.
Access and use
Part M of the Building Regulations (Doc M in the UK) governs accessible sanitary provision - turning circles, grab rails, seat heights and reach to controls. In a dwelling it also affects WC location and approach.
Worked example
A client wants a bath replaced by a level-access shower on a first floor. Work through it: check joist direction and depth for a 40 mm or 50 mm waste; confirm the fall to the stack can be achieved without cutting structure; specify a shallow trap with a good seal; tank and slope the floor; check Part M clearances and grab-rail positions. If the fall cannot be achieved, a pumped waste or a raised floor is the reasoned answer.
Traps that cost marks
Fitting a 32 mm waste to a bath; burying a trap without access; ignoring flush volume when replacing a cistern; forgetting that a shower needs a trap with an adequate seal and a floor that will not pond.