Toilet keeps running? The three parts to check first

A toilet that keeps running wastes water around the clock, and the hiss at three in the morning is usually the least of it. The good news: it is almost always one of three small parts inside the tank, and you can tell which one in a few minutes without tools.

Lift the lid and look at three things

• The fill valve — the tall assembly, usually on the left, that refills the tank after a flush.
• The flapper — the rubber seal at the bottom of the tank that lifts when you flush and drops to hold the water in.
• The overflow tube — the open pipe in the middle. If water is running into it, the tank is overfilling.

Why the toilet keeps running: read what it is doing

• Water is trickling into the overflow tube. The water level is set too high, or the fill valve is not shutting off. Lowering the float a little usually stops it; if it does not, the fill valve has worn out.
• The tank refills on its own every so often when nobody has used it — a short burst of filling in the night. That is the flapper letting water seep into the bowl until the fill valve tops it up again.
• It only stops if you jiggle the handle. The chain is too long and gets caught under the flapper, or too short and holds it open, or the flapper itself is sticking.

The dye test for a leaking flapper

Put a few drops of food coloring in the tank — not the bowl — and do not flush. Wait fifteen to twenty minutes. If color appears in the bowl, the flapper is leaking and the toilet keeps running because of it. This catches the silent leak that never makes a sound but still costs water every hour of the day.

That silent kind is also slow to show on a water bill. White Plains, for one, bills twice a year and says on its own site that leaking pipes are not the city’s responsibility; a toilet that runs continuously is one of its own examples.

Fixing it yourself

Turn off the small valve behind the toilet first, then flush to empty the tank. If that valve will not turn, do not force it — see our guide to the water shut-off valve for why.

• Chain: leave roughly half an inch of slack with the flapper closed. No more, no less.
• Flapper: take the old one to the store so the size matches. A two-inch and a three-inch flapper are not interchangeable, and the wrong one will leak from the first day.
• Float: lower it until the water stops about an inch below the top of the overflow tube.
• Fill valve: if the toilet keeps running after you adjust the float, replace the whole valve. Repairing an old one rarely lasts.

When the toilet keeps running inside the wall

A wall-hung toilet has the same parts, mounted in a tank behind the wall. The flush plate lifts off, and the fill valve and flush valve are reached through that opening. The causes are the same — a worn seal, a valve set too high — but the parts are specific to the make of the frame, so match them exactly.

When to call

Call if the toilet keeps running with new parts in, if the valve behind the toilet is seized, if water is appearing on the floor at the base rather than running inside the tank — that is a different problem — or if it is an in-wall tank you would rather not open. That is toilet repair, and it is usually a short visit.

And if no toilet is running but your water meter still turns with every faucet closed, the leak is somewhere else — that is leak detection.

KBD Plumbing & Heating works across lower Westchester — Dobbs Ferry, Hastings-on-Hudson, Irvington, Yonkers, White Plains and the rest. Licensed and insured, price agreed before work starts, and the phone is answered any hour including holidays: (914) 233-3000.

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