Why Is My Toilet Running Constantly? (Fix It in 20 Minutes)

That phantom flush sound coming from your bathroom isn't a ghost — it's a running toilet, and it's costing you money. A continuously running toilet wastes 200 gallons of water per day, which translates to $70–$200 added to your annual water bill.

The fix is almost always a simple DIY job that costs $5–$15 in parts and takes about 20 minutes.

The Two Common Causes

1. Faulty flapper: The flapper is the rubber valve at the bottom of the tank that controls water flow into the bowl. When it degrades or warps, water continuously leaks past it.

2. Float set too high: The float controls when the fill valve shuts off. If it's set too high, water rises into the overflow tube and drains constantly.

Quick Diagnosis

Remove the tank lid and observe:

• Water trickling into the bowl? → Flapper leak. Put a few drops of food coloring in the tank. If the color appears in the bowl within 15 minutes without flushing, the flapper is leaking.
• Water running into the overflow tube? → Float is set too high or the fill valve is faulty.

Fixing a Worn Flapper

1. Turn off the water supply valve (behind/below the toilet).
2. Flush to empty the tank.
3. Unhook the flapper from the overflow tube ears and disconnect the chain from the flush handle arm.
4. Take the old flapper to a hardware store to match the size, or buy a universal flapper.
5. Attach the new flapper to the overflow tube ears and reconnect the chain with 1/2 inch of slack.
6. Turn the water back on and test.

Cost: $5–$10 for a universal flapper.

Adjusting the Float

For a ball-float (older, ball on an arm): Bend the arm slightly downward to lower the float level. Water should stop 1 inch below the top of the overflow tube.

For a cup float (newer, cylindrical): Pinch the clip and slide the float down on the fill valve shaft.

When to Replace the Fill Valve

If adjusting the float doesn't stop the running, the fill valve itself may be worn. A replacement fill valve costs $10–$15 and takes about 30 minutes to install.

Still Running After These Fixes?

If the toilet keeps running after replacing the flapper and adjusting the float, the issue may be a cracked overflow tube or a problem with the flush valve seat. Describe your situation in Fixwise and our AI will walk you through the next diagnostic steps.