A running toilet wastes water every minute it runs. The EPA’s WaterSense program says an old or worn flapper alone can make a toilet flush on its own or silently leak thousands of gallons a year. The good news: you can fix it yourself, with a sponge and an adjustable wrench, in an afternoon at most.
First, look inside the tank
Lift the lid and set it somewhere safe; it’s heavy and breaks easily. You’ll see:
- The fill valve, a tall tube on the left with a float. It refills the tank.
- The overflow tube, an open pipe in the middle. Excess water drains down it into the bowl.
- The flapper, the rubber seal at the bottom, connected to the handle by a chain.
Flush once and watch what happens.
Cause 1: the flapper leaks
Signs: the toilet refills by itself every so often (a “phantom flush”), or water trickles into the bowl constantly.
Test: the EPA’s dye test. Put a few drops of food colouring in the tank and don’t flush. If colour shows up in the bowl after 10 minutes, water is leaking past the flapper. Flush afterwards so the dye doesn’t stain the tank.
Fix: turn off the water at the valve behind the toilet, flush to empty the tank, unhook the old flapper from the pegs on the overflow tube and fit a new one that matches your toilet’s flush valve size. Clean the seat it sits on first. Grit and mineral build-up stop even a new flapper from sealing. The EPA recommends checking the flapper periodically and replacing it at least every five years.
Cause 2: the chain or handle holds the flapper open
Signs: the toilet keeps running after a flush until you jiggle the handle.
Fix: the chain should have a little slack when the flapper is closed. Too tight and it holds the flapper open. Too loose and it can tangle or get caught under the flapper. Move the clip one or two links. If the handle itself sticks, tighten or replace it. On many toilets the nut inside the tank loosens the opposite way to a normal nut.
Cause 3: the water level is too high
Signs: water keeps trickling into the overflow tube and the fill valve never shuts off completely.
Fix: lower the float so the valve shuts off sooner. Most newer fill valves have an adjustment screw or clip on the float. Older ball floats have an arm you can bend down slightly. Set the water to the fill line marked inside the tank or on the valve, below the top of the overflow tube.
Cause 4: the fill valve is worn
Signs: a constant hiss, or the valve keeps running even with the water level set right.
Fix: sometimes flushing out grit helps. Follow the valve’s instructions to remove the cap and run the water briefly. Otherwise replace the whole fill valve. Kits come with instructions for setting the height, and with a refill tube that clips onto the overflow tube. Have a bucket and sponge ready to empty the tank and catch water from the supply line.
When it’s something else
- A cracked overflow tube or a worn flush valve seat means replacing the flush valve. On many toilets that means taking the tank off the bowl. It’s a bigger but still common DIY job.
- A crack in the tank or bowl means replacing the toilet. See Replace a toilet.
- The shut-off valve won’t close or leaks when you turn it: use the main water shut-off and replace the valve, or call a plumber. See How to shut off your water, power and gas.
Safety and when to call a pro
This is one of the safest jobs in the house. Wipe up water so nobody slips, and don’t over-tighten plastic nuts on the supply line, since they crack. Call a plumber if water is leaking around the base of the toilet or onto the floor below. That’s the seal between the toilet and the drain, or a supply leak, not a running toilet.
Watch it done
Our Fix a running toilet page collects step-by-step videos for flappers, fill valves and flush valves, and Toilet keeps running groups videos by symptom.
Sources
- US Environmental Protection Agency, WaterSense. Fix a Leak Week (toilet dye test and flapper replacement) Source