How Do I Fix a Toilet That Keeps Running?
Topics
- Toilet
- Running
- Flapper
- Fill Valve
- Float
Answer
A toilet that keeps running after flushing is almost always caused by one of four things: a worn flapper, a float set too high, a faulty fill valve, or a tangled lift chain. The good news is that every single one of these is a beginner-level DIY fix that takes 15–30 minutes and costs $5–25 in parts.
Step 1: Diagnose the cause
Remove the tank lid and set it aside. Flush the toilet and watch what happens:
- Press down on the flapper (the rubber disc at the bottom of the tank). If the running stops, the flapper is your problem — replace it.
- Press down on the float arm or check if water is overflowing the overflow tube. If so, the float is set too high — adjust it.
- If neither of those stops the running, you likely have a worn fill valve.
Step 2: Replace the flapper (most common fix)
Turn off the shutoff valve behind the toilet. Flush to drain the tank. The flapper unclips from the two ears on the overflow tube — no tools needed. Take the old one to the hardware store to match it, or buy a Fluidmaster 501/502 (fits most toilets). Snap the new one on and reconnect the chain with ½ inch of slack.
Step 3: Adjust the float
For a ball-and-arm style: bend the arm gently downward so the water level sits 1 inch below the overflow tube. For a cup float on the fill valve: squeeze the adjustment clip and slide it down, or turn the adjustment screw counterclockwise.
Step 4: Replace the fill valve (if needed)
Shut off water, flush tank empty. Disconnect the supply line. Unscrew the locknut under the tank (counterclockwise) and pull the old valve out. Insert the new Fluidmaster 400A or equivalent, set the height to 1 inch below the overflow tube, tighten the locknut, reconnect supply line.
The food dye test
Put a few drops of food coloring in the tank (not the bowl). Wait 15 minutes without flushing. If color appears in the bowl, your flapper is still leaking — even if it looks fine.
A running toilet wastes 200–400 gallons per day — fixing it this weekend saves real money on your water bill.
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