How to Fix a Running Toilet

A toilet that keeps running is one of the most common calls we hear about, and it's also one of the most satisfying fixes to do yourself. Nine times out of ten it's a cheap rubber part inside the tank, and you can have it handled in under half an hour with no special tools. Better yet, you'll stop it from quietly running up your water bill, which a running toilet can do to the tune of thousands of gallons a month.

First, figure out which part is failing

Take the lid off the tank and set it somewhere safe, it's heavy and it breaks. Now flush and watch what happens inside. There are really only two usual suspects:

• The flapper. That's the rubber seal at the bottom of the tank that lifts when you flush and drops back down to hold water. If it doesn't seal cleanly, water leaks past it into the bowl and the tank keeps refilling. This is the number one cause.
• The fill valve or float. That's the tall assembly on the left that refills the tank. If the water level is set too high, it never shuts off and just keeps spilling into the overflow tube (the open pipe in the middle).

The fix, step by step

1. Shut off the water. Reach behind the toilet near the floor and turn the small oval valve clockwise until it stops. Then flush to empty the tank and sponge out the last bit of water so you can work dry.
2. Replace the flapper (the most common fix). Unhook the old flapper from the two pegs at the base of the overflow tube and unclip the chain. Take it to the hardware store so you match the size and style, they're only a few dollars. Clip the new one on the same way.
3. Set the chain right. The chain from the flush handle to the flapper should have just a little slack when the flapper is down, not tight, not so long it gets trapped under the flapper. Too tight and the flapper never fully seals, which is the exact problem you're fixing.
4. Or adjust the water level. If your test pointed at the fill valve, lower the float so the water shuts off about an inch below the top of the overflow tube. Most modern valves adjust with a clip or a small screw on top of the float, older ones bend or twist.
5. If the fill valve is worn out, swap it. A fill valve that hisses, won't shut off, or is years old can be replaced as a whole unit. It's a bit more involved than a flapper but still a very doable homeowner job, and the replacement kit comes with instructions for your model.
6. Turn the water back on and test. Open the shutoff, let the tank fill, and flush a few times. You want the water to stop cleanly and the tank to go quiet. A dry, silent tank means you nailed it.

Know when to call a pro

Everything above is squarely in DIY territory. Here's where it stops being a tank-parts job:

• Water is pooling on the floor around the base of the toilet. That points to a failed wax ring or a cracked base, which means pulling the toilet, not swapping a flapper.
• You replaced the flapper and fill valve and it still leaks. Something else, like a hairline crack in the tank or a bad flush-valve seat, may be at play.
• The toilet rocks, the water supply line is corroded, or the shutoff valve won't turn or won't seal. A stuck or leaking shutoff is its own small plumbing job worth handing off.

Those are the ones where a quick look from us saves you a soaked subfloor down the line. If your running toilet is really one of these, let us get it handled right.