How to Fix a Running Toilet
A running toilet is usually caused by a worn flapper, a faulty fill valve, or a misadjusted float. The fix is simple: replace the flapper ($5–$10, 10 minutes) or replace the fill valve ($10–$20, 30 minutes). Both are easy DIY repairs that require no special tools.
Cost Breakdown
| Service | Low | High | Notes |
|---|---|---|---|
| Flapper replacement (DIY) | $5 | $10 | 10-minute fix |
| Fill valve replacement (DIY) | $10 | $20 | 30-minute fix |
| Complete rebuild kit (DIY) | $15 | $30 | Flapper + fill valve + handle |
| Professional repair | $100 | $200 | If you prefer to hire out |
Fixing a Running Toilet — Step by Step
A running toilet wastes up to 200 gallons of water per day — that can add $50–$100 to your monthly water bill. Fortunately, the fix is almost always cheap and easy.
Step 1: Identify the Cause
Remove the tank lid and observe:
- Water flowing into the overflow tube? → Float or fill valve issue
- Water seeping past the flapper? → Worn flapper
- Intermittent running (phantom flushes)? → Slow flapper leak
Step 2: Replace the Flapper (Most Common Fix)
- Turn off the water supply valve behind the toilet
- Flush to empty the tank
- Unhook the old flapper from the overflow tube and disconnect the chain
- Take it to the hardware store to match the size (or buy a universal flapper)
- Install the new flapper and reconnect the chain — leave about half an inch of slack
- Turn the water back on and test
Cost: $5–$10. Time: 10 minutes.
Step 3: Adjust or Replace the Fill Valve
If the flapper is fine but water keeps running into the overflow tube, the fill valve needs adjustment or replacement.
To adjust: Look for a screw or clip on the fill valve that controls the water level. Turn it to lower the float so water stops about 1 inch below the overflow tube.
To replace: Fill valve kits cost $10–$20 and come with instructions. Turn off water, flush, disconnect supply line, swap the valve, reconnect. Takes about 30 minutes.
When to Call a Plumber
Call a pro if you have replaced both the flapper and fill valve and the toilet still runs, if the toilet is very old and parts are no longer available, or if you notice cracks in the tank or bowl.
Related Questions
How much water does a running toilet waste?
A constantly running toilet can waste 200 gallons per day — that is 6,000 gallons per month. Even a slow leak wastes 30–50 gallons daily. Fixing it immediately saves $30–$100+ per month on your water bill.
Can a running toilet increase my water bill?
Yes, significantly. A running toilet can add $30–$100 per month to your water bill depending on the severity of the leak. It is one of the most common causes of unexpectedly high water bills.
How do I know if my toilet flapper needs replacing?
Drop a few drops of food coloring into the tank (not the bowl). Wait 15 minutes without flushing. If color appears in the bowl, the flapper is leaking and needs replacement. Most flappers last 3–5 years.