Toilet Keeps Running? $5 Fix in 10 Minutes
A running toilet wastes up to 200 gallons of water per day — adds $30+ to your monthly water bill. Plumbers charge $150–$250 to fix it. The actual job is a $5 part and takes 10 minutes. Here's how.
First: figure out which problem you have
Take the tank lid off and watch. You'll see one of three problems:
| What you see | Problem | Fix |
|---|---|---|
| Water trickles from tank into bowl | Worn flapper (most common) | Replace flapper ($5) |
| Water overflows into the tall tube in the middle | Float set too high | Adjust float (free) |
| Water never stops filling | Fill valve stuck open | Replace fill valve ($12) |
Fix #1: Replace the flapper (95% of cases)
The flapper is the rubber disk at the bottom of the tank. When you flush, it lifts and lets water rush into the bowl. When you release the handle, it should seal tight. After 5–7 years, the rubber warps and no longer seals, so water keeps trickling past it — and the tank keeps refilling to compensate.
- Shut off the water. Turn the shutoff valve behind the toilet clockwise until it stops.
- Flush the toilet to empty the tank. Sponge up residual water.
- Unclip the old flapper. It clips onto the sides of the flush valve tower. Unhook the chain from the flush lever.
- Install the new flapper (universal $3–$6 at any hardware store, or order Fluidmaster online). Clip it into place, attach the chain to the flush lever with ½ inch of slack.
- Turn water back on and let the tank fill. Flush to test. Water should stop completely within 60 seconds.
Fix #2: Adjust the float (if water is overflowing the tall tube)
The float is the plastic ball or cylinder that controls when the fill valve shuts off. If the float is set too high, the tank fills past the overflow tube, and water spills into the tube forever.
- Ball float (older toilets): Unscrew and shorten the float arm, or squeeze the arm slightly down.
- Cup float (newer toilets): Pinch the metal clip on the side of the fill valve and slide the float down the shaft. Lower by about ½ inch at a time until the water stops below the overflow tube.
- Target water level: about 1 inch below the top of the overflow tube, or wherever there's a marked water line inside the tank.
Fix #3: Replace the fill valve ($12, 15 minutes)
If water never stops running at all, the fill valve itself has failed. These wear out after about 10 years.
- Shut off water, flush to empty tank.
- Unscrew the supply hose from under the tank.
- Unscrew the lock nut under the tank (holding the old fill valve in place).
- Lift the old valve out. Drop the new one (universal Fluidmaster 400A or similar) through the same hole.
- Tighten lock nut, reconnect supply hose, turn water on, adjust float, test.
Not sure which part to buy?
Photograph inside your tank. Our AI matches the exact flapper or fill valve for your toilet model.
Diagnose my toilet free →Frequently asked questions
How much water does a running toilet waste?
Up to 200 gallons per day, which can add $30–$50 to your monthly water bill. That's roughly $400–$600 per year — worth 10 minutes to fix.
Why does my toilet sometimes run on its own?
Called "ghost flushing" — the flapper is leaking slowly, so the tank silently loses water over an hour, then the fill valve kicks on to refill. Replace the flapper.
Do I need a specific brand of flapper?
Most Kohler, American Standard, and TOTO toilets use universal flappers. Some high-efficiency models (especially dual-flush) need brand-specific parts — check your toilet model number on the inside of the tank wall.
Can I use a toilet that's running?
Yes — it still flushes. But the waste adds up fast. Fix within a few days.