Homeowner guide · Tank talk
Fixing a Running Toilet
A toilet that keeps hissing or refilling on its own is not just annoying. It quietly sends water down the drain all day and night. The fix is usually simple and inexpensive.
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Jump to a section
- Listen and look
- Flapper problems
- Fill valve adjustments
- When to replace parts
Quick checklist
Have these on hand
- Bucket and old towels
- Flashlight or headlamp
- Adjustable wrench and channel-lock pliers
- Rubber gloves
Stop and call when
- Water is coming through a ceiling
- A drain is backing up into the basement
- There is a gas odour: get outside before phoning anyone
- A fitting will not loosen without twisting the pipe behind it
Listen and look
Lift the tank lid off and set it somewhere safe; it is heavy and breaks easily. Flush once and watch the parts work. You will see the handle lift a chain, the chain lift a rubber flapper, water rush into the bowl, the flapper drop, and the fill valve refill the tank until the float reaches its set level.
A running toilet is almost always one of three things:
- The flapper is not sealing, so water leaks into the bowl.
- The fill valve is set too high, so water spills into the overflow tube.
- The chain is too short, too long or tangled.
Flapper problems
Rubber flappers age. They warp, stiffen and pick up mineral deposits, especially in hard water areas. When that happens, they no longer seal against the flush valve seat.
- Shut off the water at the valve behind the toilet and flush to empty the tank.
- Unhook the flapper from the ears on the overflow tube and the chain from the handle.
- Inspect it. If it is soft, warped or cracked, replace it.
- Wipe the seat smooth with a cloth or a soft scrub pad.
- Carry the old flapper with you to the store so the size matches, usually two or three inches.
Use the dye test from our hidden leak guide to confirm the new one seals.
Fill valve adjustments
Look at the water line in the tank. It should sit roughly an inch under the top of the overflow tube, often marked on the inside of the tank. If water is pouring into the overflow tube, the fill valve sits too high.
On a float-cup valve, turn the adjustment screw or pinch the clip and slide the cup down. On older ball-float valves, gently bend the arm downward or turn the screw on top. Flush and watch until the level settles below the overflow.
If the fill valve hisses, refills in short bursts, or will not shut off at all after adjustment, the internal seal is worn. Replacement fill valves are standard and come with instructions.
When to replace parts
Replace the flapper first, since it is the most common culprit and the cheapest part. If the fill valve keeps acting up, change that next. When you find corrosion on the tank bolts, a cracked tank, or a worn flush valve seat, the repair becomes bigger. At that point a professional toilet repair, or even a new toilet installation, may make more sense. Pressure problems can also stress fill valves; see our water pressure guide.
Aurora customers often ask
Why does my toilet refill by itself now and then?
Plumbers call that phantom flushing. It usually means the flapper is leaking slowly, letting the tank level drop until the fill valve kicks in.
Can I use any flapper on my toilet?
Flappers come in different sizes and styles. Match the size and check the manufacturer's recommendations for your model.
How long does a toilet flapper last?
It varies with water quality and use. Many need replacing every few years, sooner with hard water or chlorine tablets in the tank.