If you need to know how to fix a running toilet, you’re in the right place — and acting fast will save you money. A running toilet can waste hundreds of gallons of water a day. The good news? It’s one of the easiest fixes in the house, and you can probably handle it in under 30 minutes with no plumbing experience whatsoever.

What’s Actually Causing It

Most running toilets come down to one of three things: a worn flapper, a float set too high, or a faulty fill valve. Don’t let the terminology scare you — once you open the tank lid and take a look, it’ll make sense immediately. The flapper is the rubber seal at the bottom of the tank. The float is the balloon-looking thing that rises with the water level. The fill valve is what refills the tank after you flush.

What You’ll Need

You’ll need a replacement flapper (about $5 at any hardware store), an adjustable wrench, and maybe 20 minutes. That’s genuinely it. Most flappers are universal, but if you want to be sure, bring your old one to the store or look up your toilet model number (usually stamped inside the tank).

Step 1 — Check the Flapper First

Lift the tank lid and set it aside carefully — it’s heavy ceramic and will crack if dropped. Push down on the flapper with your finger while the toilet is running. If it stops running, the flapper is your problem. Turn off the water supply valve (the knob on the wall behind the toilet), flush to empty the tank, then unhook the old flapper from the two side pegs and disconnect the chain from the flush handle arm. Snap the new one on, reconnect the chain (leave a little slack), turn the water back on, and you’re done.

Step 2 — Check the Float

If the flapper isn’t the issue, check whether water is flowing into the overflow tube — the tall tube in the center of the tank. If it is, your float is set too high. On a ball float (the old-school balloon style), bend the arm down slightly. On a cup float (the newer cylinder style), there’s usually an adjustment screw or clip you can slide down. The water level should sit about an inch below the top of the overflow tube.

Step 3 — Replace the Fill Valve If Needed

If neither of those fixed it, the fill valve probably needs replacing. This sounds scarier than it is. Turn off the supply valve, flush to drain the tank, use a wrench to disconnect the supply line under the tank, unscrew the locknut holding the fill valve, swap in a new universal fill valve (about $12), and reverse the steps. There are great YouTube videos for your specific toilet model if you want a visual walkthrough.

You’ve Got This

A running toilet is one of those repairs that sounds plumbing-level intimidating but is really just a parts swap. Most people fix it on their first try. If you’re still hearing running after trying all three steps, that’s when it’s worth calling a plumber — but that’s genuinely rare.

Just moved into a new home? Check out our guide on what to do when you move into a new house.

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