Fix a Toilet That Won't Stop Running

A running toilet can waste hundreds of gallons of water per day and drive up your water bill. The good news is that fixing it is often a straightforward task anyone can tackle in 15-20 minutes by diagnosing and addressing the most common causes.

Diagnose First (Free)

1. Remove tank lid and look inside while it's running
2. Check the flapper: At the bottom of the tank, does the rubber flapper seal tightly over the flush valve? If water is trickling past it into the bowl, that's your culprit (most common cause)
3. Check the fill valve: Is water continuously running into the overflow tube (the tall pipe in the center)? If yes, the fill valve isn't shutting off properly
4. Check the float: Is the float stuck or sitting too high? It should stop rising when water reaches about 1 inch below the overflow tube
5. Check the chain: Is the chain connecting the flush handle to the flapper too short, tangled, or too long? This can prevent proper sealing

The Fix (Pick One Based on What You Found)

Problem 1: Flapper Not Sealing (Most Common)

1. Turn off water supply valve behind toilet (turn clockwise)
2. Flush to drain tank completely
3. Unhook old flapper from overflow tube ears and disconnect chain
4. Take old flapper to a hardware store like Walmart or a local hardware store to match it, or buy a universal flapper
5. Install new flapper—hook it onto the overflow tube ears and attach chain with about 1/2 inch of slack
6. Turn water back on and test flush to ensure proper sealing

Problem 2: Fill Valve Won't Shut Off

1. Turn off water supply valve
2. Flush to drain tank
3. Unscrew fill valve locknut under the tank (use adjustable wrench or pliers)
4. Lift out old fill valve
5. Install new fill valve following manufacturer instructions—hand-tighten locknut and adjust height so the critical line is about 1 inch above the overflow tube
6. Reconnect refill tube to overflow tube
7. Turn water on and adjust float so water stops about 1 inch below the top of the overflow tube

Problem 3: Float Level Too High

• Adjust the float by bending the float arm downward (for older ball-style floats) or adjusting the clip/screw on newer column-style floats
• Water level should be about 1 inch below the overflow tube opening

Problem 4: Chain Issues

• Adjust chain to have about 1/2 inch of slack when flapper is closed
• Clip excess chain length so it doesn't get stuck under the flapper or tangle
• Ensure chain isn't too short, which prevents the flapper from sealing completely

When to Call a Plumber

• Water is leaking from tank bolts or the base of the toilet (needs resealing or wax ring replacement)
• The flush valve itself is cracked (requires more extensive disassembly)
• After systematically inspecting and replacing parts, the toilet still runs
• You're not comfortable working with plumbing components

Pro tip: Most toilet parts are universal and inexpensive ($5-$15), available at Walmart, Best Buy, or local hardware stores. Take your old part with you to match it if uncertain. Fluidmaster is a trusted brand for fill valves and flappers. Address this issue promptly to stop water waste and prevent higher utility bills.