How to Fix a Running Toilet
Learn how to fix a running toilet in under 30 minutes. Covers the flapper, fill valve, and float with no special tools required.
We ignored a running toilet for three months once. The sound was annoying, but it seemed like a plumber problem. Then we saw the water bill. Turns out a running toilet can waste 200 gallons a day. That is not a typo.
Almost every running toilet comes down to one of three parts inside the tank. The flapper, the float, or the fill valve. All of them are cheap, easy to find at any hardware store, and straightforward to replace.
You do not need to be handy. You do not need special tools. If you can turn a valve and follow directions, you can fix this in less time than it takes to wait for a plumber to call you back.
This guide walks through the causes in order of likelihood, so work down it and stop when the noise stops.
You will need a pair of rubber gloves if you are squeamish about reaching into the tank (the water is clean, but we get it). A sponge or old towel helps mop up any small spills. Replacement flappers cost about $5 to $8 at any hardware store. If your fill valve needs replacing, a universal kit runs about $10 to $15. An adjustable wrench may be helpful but is not always necessary.
Turn off the water and open the tank
Find the shut-off valve behind the toilet near the floor. Turn it clockwise until it stops. Then flush the toilet once to drain most of the water from the tank. Lift the tank lid straight up and set it somewhere safe on a towel. Tank lids are heavy ceramic and crack easily if they hit tile. Look inside the tank. You will see a rubber flapper at the bottom connected to a chain, a tall tube in the center called the overflow tube, and a fill valve assembly on the left side.
Check the flapper for wear
The flapper is the round rubber piece that covers the drain hole at the bottom of the tank. Reach in and feel it. If it is warped, cracked, slimy, or does not feel smooth, it is not sealing properly and water is leaking into the bowl. This is the most common cause of a running toilet. Unhook the flapper from the pegs on either side of the overflow tube, disconnect the chain from the flush lever, and bring it to the hardware store to match the size.
Good to know: Drop a few drops of food coloring into the tank water and wait 15 minutes without flushing. If the color appears in the bowl, the flapper is definitely leaking. This confirms you have found the right problem before buying parts.
Install a new flapper
Hook the new flapper onto the same pegs on the overflow tube. Reconnect the chain to the flush lever arm, leaving about half an inch of slack. Too much slack and the flapper will not lift fully when you flush. Too little slack and it will not sit flat to seal. Turn the water back on and let the tank fill. Flush once and watch the flapper close. If it seals flat and the water stops running, you are done.
Adjust the float if the water level is wrong
If the flapper is fine, the problem might be the water level. Look at the overflow tube. There is usually a line or marking showing the correct water level, typically about an inch below the top of the overflow tube. If water is flowing into the overflow tube, the float is set too high. On a ball float, bend the metal arm down slightly. On a cylinder float, squeeze the clip and slide the float down the rod about half an inch. Flush and check the new water level.
Heads up: If water is actively flowing over the top of the overflow tube, the float adjustment is your fix. Do not ignore this. Constant overflow into the tube is what causes the fill valve to run endlessly and wastes the most water.
Replace the fill valve if adjustments do not help
If the flapper is good and the float is adjusted correctly but the toilet still runs, the fill valve itself is worn out. Turn off the water and flush to empty the tank. Use a sponge to remove remaining water. Disconnect the water supply line from below the tank. Unscrew the lock nut holding the fill valve in place. Pull out the old valve and install the new one following the kit directions. Most universal fill valve kits fit all standard toilets. Reconnect the supply line, turn the water on, and check for leaks.
Test everything and clean up
Let the tank fill completely. Flush two or three times and listen. You should hear the tank fill and then stop completely with no hissing, trickling, or phantom refilling sounds. Put the tank lid back on. Turn the shut-off valve back to fully open if you tightened it down earlier. Wipe up any water on the floor. The whole job typically takes 15 to 25 minutes once you have the right parts.
That is it. The flapper, the float and the fill valve are the whole list for a tank that will not stop running. We have fixed four toilets this way across different apartments and houses, and it has never taken more than 20 minutes. If you tried all three and the toilet is still running, the issue might be a cracked overflow tube or a problem with the tank itself. At that point, calling a plumber is reasonable. But the usual outcome is a $5 flapper and one short job with the water shut off. Dealing with a clog instead of a running toilet? We have a separate guide on how to unclog a toilet that covers every method from plunging to using a toilet auger.
Questions we get asked about this
Answers from experience, not a textbook.
This is called phantom flushing and it almost always means the flapper is leaking slowly. Water seeps from the tank into the bowl until the level drops enough to trigger the fill valve. The fill valve runs for a few seconds to top off the tank, and the cycle repeats. Replace the flapper and the phantom flushing will stop.
A continuously running toilet can waste 6,000 gallons per month or more. At average US water rates, that is an extra $50 to $100 per month depending on your area. Even a slow leak from a worn flapper can waste 30 to 50 gallons a day. The $5 to $15 fix pays for itself immediately.
Universal flappers work for most standard toilets. They come in 2-inch and 3-inch sizes. Bring your old flapper to the hardware store to match the size. Some newer toilets, especially dual-flush models, use proprietary flappers. If a universal one does not fit, check the toilet manufacturer's website for the correct part number.
Yes. The water in the tank is the same clean water that comes out of your faucets. It has not contacted the bowl. It is perfectly safe to reach in without gloves, though some people prefer to wear them anyway. Just wash your hands afterward.
Some older homes have the shut-off valve behind an access panel or inside the wall. If you truly cannot find one, you can shut off the main water supply to the house temporarily. Turn on a faucet elsewhere in the house to confirm the water is off before working on the toilet. Aim to add a dedicated shut-off valve later for convenience.
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