Toilets, cisterns and overflows in Barnet, Finchley and Edgware

Why is water dripping from a pipe on the outside wall?

Older cisterns have a warning pipe that passes through the wall and ends outdoors, often just above a window or near the ground. When the valve that refills the cistern fails to shut, the level rises until water spills into that pipe and drips outside. In winter the drip can freeze on a path, and in a flat it may land on the balcony or the window of the home below.

Modern cisterns often do without the outside pipe. Their overflow runs down into the pan instead, so an over-filling cistern shows as a trickle in the bowl that never quite stops.

What is going wrong inside the cistern?

Lift the lid and watch. If the water creeps above the line marked inside the cistern, the inlet valve or its float is at fault. If the level stays put but water still moves in the pan, the seal at the base of the cistern is letting water through. Limescale is behind many of these faults, because the water in this part of London is hard, and a seal coated in scale cannot close cleanly.

A plumber can change the inlet valve, the seal or the whole flush mechanism without disturbing the pan, provided parts for your model are still made. For a very old cistern, a new one is sometimes the simpler route.

Why has the flush gone weak?

A weak flush is not always a blockage. Common reasons include:

• a flush valve that opens only part way because the button linkage has slipped
• a cistern that is not filling to the right level, so less water is released
• scale under the rim of the pan, blocking the holes the water comes out through
• a siphon in a lever-operated cistern whose diaphragm has split

If the toilet fills up, empties slowly and then clears, that is a blockage in the pan or the branch pipe, which is a different fault.

Is a toilet in a flat any different?

In a converted house or a block, several toilets discharge into one soil stack. A blockage further down can make a toilet on a lower floor fill or gurgle when a neighbour flushes, and a shared stack is usually the freeholder's or the management company's to maintain. Say whether other flats seem to be affected and whether the stack is inside or outside the building.

Many flats in the borough have a cistern hidden behind a panel or inside a cupboard. Access is the first question for a plumber, so mention where the cistern is and whether the panel comes off.

Why is the floor around the pan wet?

Water on the floor can come from a few places and they are worth telling apart:

• condensation on a cold cistern in a steamy bathroom, which forms droplets on the outside
• a weep from the joint between cistern and pan, which shows up only after a flush
• the pan connector at the back, where the pan joins the soil pipe, which can let foul water out and is a health matter as well as a plumbing one
• a cracked pan, which is rare but means replacement

A pan that rocks has usually lost its fixings or the sealant beneath it. Left alone, the movement works the connector loose.

Can a toilet go where there is no soil pipe?

Yes, within limits. A macerator unit grinds waste and pumps it along a small-bore pipe to the nearest stack, which is how many downstairs cloakrooms and loft en suites in the borough's extended houses were fitted. They need power, a run of pipe that stays inside the maker's limits and regular care, and they cannot cope with wipes or sanitary products. A plumber can tell you whether a conventional connection is possible instead, which is usually the better answer where it can be done.

Altering drainage can come under the Building Regulations, so ask the plumber whether the work needs to be notified to the council's building control service or a registered building control approver.

Is there a limit on how much a toilet flushes?

Yes. The Water Supply (Water Fittings) Regulations 1999 cover new toilets, among other fittings connected to the mains supply, and since 2001 a newly installed cistern has been limited to a single flush of 6 litres, which is why nearly every toilet sold now has a dual flush button. A plumber will supply a cistern that complies if yours is being replaced.

What is useful to mention?

• your postcode
• what the toilet is doing: dripping outside, running, slow to fill, weak, rocking or leaking at the base
• whether the cistern is exposed, boxed in or set into a wall
• whether a small isolating valve lets you shut the water off to that fitting
• in a flat, whether neighbours have the same trouble
• the make, if it is printed inside the lid, which helps with parts