Toilet Keeps Running: How to Find the Cause and Fix It
A toilet that keeps running wastes water and is hard to ignore. The cause is usually one of a few small parts inside the tank. This guide walks through the simple checks in a sensible order, what not to do, and when it's time to call a plumber. LocalRepairLine is a referral service, not a contractor, and this is general information, not a substitute for an in-person inspection.
Before you start
A running toilet is usually a simple tank problem, and you can stop the water in seconds with the shut-off valve on the wall behind the toilet. Turn it clockwise. If water is leaking onto the floor or the valve won't turn, stop and call a plumber. Don't use harsh chemical drain cleaners in a toilet.
Why a toilet keeps running
- Worn or misaligned flapper. The rubber flapper at the bottom of the tank doesn't seal, so water keeps leaking into the bowl and the tank keeps refilling.
- Flush chain too tight or too loose. A tight chain holds the flapper open slightly, and a tangled one can keep it from closing.
- Water level set too high. Water spills into the overflow tube and the fill valve never shuts off.
- Faulty fill valve. The valve that refills the tank can wear out and fail to stop the flow.
- Mineral buildup. Deposits on the flapper seat can stop a good seal.
Simple checks and fixes
- Lift the tank lid and look. Is water flowing into the overflow tube, or can you hear a hiss?
- Jiggle the handle. If the running stops, the chain or handle is the likely cause. Adjust the chain so it has a little slack, about half an inch.
- Do a dye test. Add a few drops of food coloring to the tank, don't flush, and wait about 15 to 20 minutes. If color shows up in the bowl, the flapper is leaking.
- Check the water level. It should sit about an inch below the top of the overflow tube. Many fill valves have an adjustment screw or a float you can lower.
- Wipe the flapper seat. Turn off the supply valve, flush to empty the tank, and gently clean the seat and flapper with a cloth.
- Replace the flapper if it's soft, warped or cracked. Take the old one to a hardware store to match the size and style. Most replacements take a few minutes with no special tools.
- Replace the fill valve if the level won't stay adjusted or it keeps hissing. If you aren't comfortable doing this, a plumber can do it quickly.
What not to do
- Do not ignore a toilet that runs all day. It wastes water and can raise your bill.
- Do not force a shut-off valve that won't turn.
- Do not drop cleaning tablets into the tank. They can damage rubber parts.
- Do not overtighten the bolts on the tank, which can crack the porcelain.
When to call a plumber
- Water leaks at the base of the toilet, at the tank bolts or from the supply line.
- The tank or bowl is cracked.
- The shut-off valve won't close or is corroded.
- The toilet still runs after you replaced the flapper and checked the fill valve.
- The toilet is clogged or backs up in addition to running.
What to tell the plumber
- Whether the toilet runs constantly or only refills by itself every so often.
- What you tried: chain adjustment, water level, flapper, fill valve.
- The age and approximate make of the toilet, if you know.
- Whether there's any leak on the floor.
Need a plumber?
Describe the problem to an independent local plumbing company. A short automated prompt plays first, and then you're connected. LocalRepairLine is a referral service, not a contractor.
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