Keeping connections accessible, joints aligned and sealed properly, pans matched to cisterns, and appliances fixed so nothing leaks.
Keep connections accessible
Keep traps, connections and the required branch access within reach, so you can inspect and clean them. A removable trap or access cap can save you cutting into finishes. The right way to clear a blockage still depends on what it is and on the pipe's condition. Where boxing-in would hide them, fit removable panels.
Align and support every joint
Choose a WC pan connector that suits the outlet positions, including any designed offset. Fit and support it as its manufacturer says. Forcing or twisting a connector into place strains the seal. The joint can then leak foul water or narrow the bore.
If a joint like this starts to weep, inspect it and remake it with the specified seals and sound, correctly aligned parts. The fitting instructions may call for sealant at a particular joint face. Sealant smeared round the outside of a failed joint will not fix a poor fit or a damaged seal.
Match the pan, cistern and pipework to the appliance
A WC pan is designed to clear fully with a particular cistern's flush volume and pattern. Pair it with the wrong cistern and it can leave waste behind or need flushing again and again.
Waste pipe material matters too. Some plastics soften or distort when the discharge is hotter than they are rated for. That strains the joints and causes leaks. So choose a material that suits what the appliance actually discharges.
Approved Document H's pipework guidance assumes WCs with a major flush of at least 5 litres. A smaller flush carries solids a shorter distance, so where a WC flushes less, allow for a greater risk of blockages. BS EN 12056 covers pipework for major flushes down to 4 litres.
Fix appliances securely
Fix every appliance firmly enough that normal use cannot move it. An appliance that rocks in use, such as a basin someone leans on, strains its supply and waste joints until they leak.
Where Approved Document G puts the appliances
Every house or flat needs at least one WC with a hand-washing facility. Requirement M4(1) puts that WC on the principal or entrance storey.
Each additional WC needs its own hand-washing facility, in one of two places:
- in the WC's room;
- in a room or lobby that is the only way into the WC.
It never goes in a place used for preparing food.
A door separates any room holding a WC or its basin from a kitchen or other food preparation area. In a house:
- a room holding both the WC and its basin needs only that door, not a lobby;
- where the room holds only the WC, its basin goes in a space between that room and the kitchen, with a door between that space and the kitchen.
Every house also needs at least one bathroom with a washbasin and either a fixed bath or a shower. Every kitchen needs a sink. Where an appliance has separate hot and cold taps, the hot tap goes on the left.
WCs with a macerator
Approved Document G allows a WC with a macerator and pump to discharge through small-bore pipework to a discharge stack. Two conditions apply:
- there is also access to a WC that discharges directly to a gravity system;
- the unit meets BS EN 12050-1 or BS EN 12050-3.
Stuart Turner's FAQ says its Wasteflo WC macerators must not take a bath's waste. A bath empties so much water at once that it can force open the non-return valves in the unit's inlets. Macerator water could then flow back into the bath. The smaller flows from a shower or a basin do not do this. Where a bath waste has to be pumped, send it to a lifting station instead.
Washing machines: use an open, trapped standpipe
For a standpipe, use an open, trapped connection. Follow the machine's instructions for hose height, insertion depth and fixing.
- The trap's water seal stops foul air coming back.
- The open top lets air in around the hose.
- A hose fitted too low can let the machine empty while it fills.
- Keep the hose outlet clear of standing wastewater. If the outlet sits in it, dirty water can flow back.
A blockage can still back water up to the hose, even with a loose fit at the top.
A manufacturer may also allow connection to a suitable appliance spigot on a trapped sink waste. That is different from an untrapped direct connection. Follow the arrangement allowed for the machine, including securing the hose and preventing kinks.