You hear it from down the hall: the toilet hissing and refilling long after anyone flushed. A running toilet can waste a lot of water and run up your bill. The good news is that the fix is almost always a cheap part and about twenty minutes of your time. No plumber needed.

First, Find the Cause

Take the lid off the tank and set it somewhere safe, since it’s heavy and breaks easily. Nearly every running toilet comes down to one of three things.

1. The Flapper Isn’t Sealing

The flapper is the rubber cover at the bottom of the tank. When it gets old, warped, or dirty, water leaks past it into the bowl, and the tank keeps refilling to make up the difference. This is the most common cause.

Quick test: Put a few drops of food coloring in the tank water. Don’t flush. Wait about 15 minutes. If color shows up in the bowl, the flapper is leaking.

2. The Chain Is the Wrong Length

The chain connects the flush handle to the flapper. Too short, and it holds the flapper open. Too long, and it can get caught underneath the flapper. You want just a little slack when the flapper is closed.

3. The Water Level Is Too High

Look at the tall open tube in the middle of the tank. That’s the overflow tube. If water is spilling into it, the tank is filling too high and draining the extra into the bowl nonstop. Many tanks have a water line marked on the inside; if yours doesn’t, the water should stop about an inch below the top of the overflow tube.

How to Fix Each One

Chain: Unhook it and move it to a different link so there’s a bit of slack. Flush a few times to make sure the flapper drops closed every time.

Water level: Find the float on the fill valve (the tall part on the left side of most tanks). Most newer fill valves have an adjustment screw or clip that lowers the float. Lower it a little, flush, and check the level again.

Flapper: Turn off the water at the valve behind the toilet, then flush to empty the tank. Unhook the old flapper and take it with you to the hardware store so you can match it. Flappers are inexpensive and snap right on.

Still Running?

If a new flapper and a correct water level don’t stop it, the fill valve itself may be worn out. Replacing it is a bigger job, but still very doable at home. My guide walks you through fixing a running toilet, step by step.

Get the full guide: How to Fix a Running Toilet by Hank Palmer, on Amazon