Toilet Keeps Running: How to Fix a Running Toilet
A running toilet wastes up to 200 gallons of water per day and is one of the most common home plumbing issues. In most cases, the fix costs $5–$15 and takes under 30 minutes. The culprit is almost always a worn flapper valve, an incorrect float height, or a tangled flush chain — all simple DIY repairs.
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Common Symptoms
- Toilet hisses or runs continuously after flushing
- Toilet turns on and off periodically on its own ('phantom flush')
- Water runs into the bowl long after the tank fills
- Tank never fully fills and keeps running
- Water bill is higher than usual
Most Likely Causes
- 1
Worn Flapper Valve (Most Common)
The flapper is the rubber valve at the bottom of the tank that seals against the flush valve seat. Over time it warps, deteriorates, or gets coated with mineral buildup, preventing a proper seal. Water slowly leaks into the bowl, and the fill valve keeps running to compensate. This is the most common running toilet cause.
- 2
Float Set Too High
If the water level in the tank rises above the overflow tube, water continuously drains into the bowl and the fill valve keeps refilling. Adjusting the float down 1/2 inch below the top of the overflow tube immediately stops this.
- 3
Faulty or Worn Fill Valve
The fill valve refills the tank after each flush. When the fill valve wears out, it may not shut off completely — letting a small trickle of water continuously flow into the tank and out through the overflow. A complete fill valve replacement costs about $12.
- 4
Flush Chain Too Short or Tangled
If the chain connecting the flush handle to the flapper is too short, kinked, or tangled, it can hold the flapper slightly open all the time — causing a constant slow leak into the bowl. Adjust the chain to have 1/2 inch of slack.
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Quick DIY Checks
- 1Remove the tank lid and observe: if water is flowing over the top of the overflow tube, the float is set too high. Adjust the float arm or turn the adjustment screw on the fill valve until the water level is 1/2 inch below the top of the overflow tube.
- 2Test the flapper: add a few drops of food coloring to the tank water. Wait 15–20 minutes without flushing. If colored water appears in the bowl, the flapper is leaking and needs replacement.
- 3Check the chain: it should have about 1/2 inch of slack. If it's too short (holds flapper open) or too long (gets caught under the flapper), adjust the clip position on the flush handle arm.
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Try Pro — $7.99/mo- 4Replace the flapper: turn off the water supply (valve behind the toilet), flush to empty the tank, unhook the old flapper from the overflow tube ears, and snap the new one on. Turn water back on and test.
- 5If the running persists after flapper replacement, replace the fill valve ($10–$15 complete kit). Fluidmaster 400A is the industry standard — it takes about 20 minutes to swap.
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Repair vs Replace
A running toilet is one of the most cost-effective home repairs available. A flapper costs $5–$8 and takes 10 minutes. A complete fill valve kit runs $10–$15. Even replacing both together costs under $25 and takes under an hour. Toilet replacement is only warranted if the porcelain is cracked or there are multiple simultaneous plumbing failures.
Est. Repair Cost
$5–$30 in parts
Est. Replacement Cost
$200–$500 for a new toilet
Recommended Tools & Parts
- Buy on Amazon →
Universal Toilet Flapper
Universal rubber flapper that fits most standard toilets. Replace when leaking or running won't stop.
$5–$10
- Buy on Amazon →
Fluidmaster 400A Fill Valve
The most popular toilet fill valve replacement. Adjustable height fits most tanks and installs in 15 minutes.
$10–$15
- Buy on Amazon →
Toilet Tank Repair Kit
Complete repair kit including flapper, fill valve, and flush valve. Fixes running, phantom flush, and slow fill.
$15–$25
Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.
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Read guide →Save $150+ on a single service call
Less than a cup of coffee — fix it yourself with expert guidance.
- ✓ Step-by-step repair guides with exact part numbers
- ✓ Expert diagnosis in seconds — 500+ problems covered
- ✓ Full tool list & cost estimate before you spend a dime
$150+ service call vs. $7.99/mo · Cancel anytime
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