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A toilet that keeps running is easy to ignore and expensive to live with. A leaking flapper can waste hundreds of gallons a day, and it shows up on the water bill long before it shows up on the floor. The good news is that there are only a few parts inside a toilet tank, and you can usually find the culprit in five minutes.
How a toilet tank works
When you flush, a rubber flapper at the bottom of the tank lifts and lets the water into the bowl. The flapper drops back, and a fill valve refills the tank until a float tells it to stop. A running toilet means one of two things: water is leaking out of the tank past the flapper, or the fill valve is not shutting off.
The dye test
Take the lid off the tank and add a few drops of food coloring to the water. Do not flush. Wait fifteen to thirty minutes. If color appears in the bowl, water is leaking past the flapper. If the bowl stays clear, look at the fill valve and the water level instead.
Cause 1: A worn flapper
This is the most common cause by a wide margin. The rubber hardens, warps or gets coated with mineral scale, and it stops sealing. Replacement flappers are inexpensive. Shut off the valve behind the toilet, flush to empty the tank, unhook the old flapper and take it with you to match the size, because two-inch and three-inch flappers are not interchangeable.
Cause 2: The chain is the wrong length
A chain that is too short holds the flapper slightly open. A chain that is too long can get caught under the flapper. There should be about half an inch of slack when the flapper is closed.
Cause 3: The water level is too high
If the water in the tank rises above the top of the overflow tube, it runs down the tube into the bowl constantly. The level should sit about an inch below the top of the tube. Most fill valves have an adjustment screw or a clip on the float to lower it.
Cause 4: A failing fill valve
If the level is set correctly and the valve still hisses, trickles or never quite shuts off, the fill valve is worn. Replacing one is a manageable job if the shut-off valve behind the toilet works. If that valve is seized or drips when you turn it, stop there. Forcing an old shut-off is how a small repair becomes a wet floor.
The toilet that refills by itself
If the toilet runs for a few seconds every so often when nobody has used it, plumbers call it a phantom flush. The tank is slowly leaking into the bowl until the fill valve tops it up. The cause is almost always the flapper or the flush valve seat it rests on.
When to call a plumber
- A new flapper did not stop the leak. The flush valve seat may be pitted or cracked.
- The shut-off valve behind the toilet will not turn or leaks.
- There is water on the floor around the base of the toilet.
- The tank or bowl has a visible crack.
Common questions
How much water does a running toilet waste?
It depends on the leak, but a flapper that does not seal can waste two hundred gallons a day or more. A toilet that runs constantly wastes far more than that.
Can I just jiggle the handle?
It works for the moment because it reseats the flapper. It also tells you the chain or the flapper needs attention.
We fix running toilets, leaking faucets and worn valves across Macomb County. See our plumbing repair service or call (586) 943-4158 for a free estimate.
