How to Fix a Running Toilet

A toilet that keeps running wastes water and can quietly raise your water bill. The good news is that the cause is almost always inside the tank, and most fixes need only a few minutes and an inexpensive part from a hardware store. Here is how to find the problem and solve it.

Get to Know the Tank

Lift the tank lid and set it somewhere safe, since it is heavy and breaks easily. Inside you will see a few key parts:

• Flapper: the rubber seal at the bottom that lifts when you flush.
• Chain: connects the flush handle lever to the flapper.
• Overflow tube: the open vertical pipe in the middle of the tank.
• Fill valve and float: the tall assembly that refills the tank and shuts off when the float rises.

Find the Cause

1. Flush and watch the tank refill. If water keeps pouring into the overflow tube, the water level is set too high or the fill valve is not shutting off.
2. If the water level is below the top of the overflow tube but the toilet still runs or refills on its own every so often, the flapper is probably leaking.
3. To confirm a flapper leak, add a few drops of food coloring to the tank and wait about 15 minutes without flushing. Color in the bowl means water is slipping past the flapper.

Fix the Chain and Flapper

1. Check the chain first. It should have just a little slack. Too tight and the flapper cannot seal; too loose and it can get caught underneath. Adjust it by moving the clip to a different link.
2. If the chain is fine, turn off the water at the shutoff valve behind the toilet by turning it clockwise.
3. Flush to drain the tank and sponge out any remaining water.
4. Unhook the old flapper from the pegs on the overflow tube and the chain from the lever.
5. Wipe the valve seat clean, then install a new flapper that matches your toilet’s flush valve size, usually 2 or 3 inches. Bring the old one to the store if unsure.
6. Reattach the chain, turn the water back on, and test a few flushes.

Adjust or Replace the Fill Valve

1. The water should stop about an inch below the top of the overflow tube. If it is higher, lower the float. On most modern valves, you squeeze a clip or turn an adjustment screw to slide the float down.
2. Flush and check the new level. Make small adjustments until it shuts off at the right height.
3. If the valve still hisses or will not shut off, replace it. Turn off the water, drain the tank, disconnect the supply line under the tank, unscrew the locknut, and install a new universal fill valve following its instructions.
4. Make sure the refill tube clips onto the overflow tube, then turn the water on and check for leaks under the tank.

Quick Tips

• Hand-tighten plastic nuts and add only a small extra turn with pliers to avoid cracking them.
• Keep a towel on the floor while working to catch drips.
• If the tank itself is cracked or the shutoff valve will not close, call a plumber.