How to Fix a Running Toilet
Stop that constant running sound and save up to $200 per year on your water bill. This beginner-friendly guide covers the three most common causes and how to fix each one in under 30 minutes.
Repair & Refinish Team
Published January 15, 2026 · Updated March 10, 2026
What You'll Need
- Adjustable wrench
- Tongue-and-groove pliers
- Sponge or towel
- Bucket
- Rubber gloves
- Universal toilet flapper
- Fill valve replacement kit (if needed)
- Toilet tank repair kit (optional all-in-one)
Cost Estimate
Budget
$5
Mid-Range
$15
Premium
$30
A plumber typically charges $150-$300 for this repair. DIY cost is $5-$30 for parts.
Step-by-Step Instructions
Diagnose the Problem
Step 1 of 6Remove the tank lid and set it aside on a towel (porcelain chips easily). Flush the toilet and watch what happens. If water keeps flowing after the tank fills, note whether it's leaking past the flapper into the bowl (flapper issue), overflowing into the overflow tube (float issue), or the fill valve never shuts off (fill valve issue).
Add a few drops of food coloring to the tank water and wait 15 minutes without flushing. If color appears in the bowl, your flapper is leaking.
Shut Off the Water Supply
Step 2 of 6Locate the shut-off valve on the wall behind and below the toilet. Turn it clockwise until it stops. Flush the toilet to drain the tank. Use a sponge to soak up any remaining water in the bottom of the tank.
Replace the Flapper (Most Common Fix)
Step 3 of 6Unhook the old flapper from the overflow tube ears — it usually just unclips. Disconnect the chain from the flush lever. Take the old flapper to the hardware store to match the size, or use a universal flapper. Attach the new flapper to the overflow tube ears, reconnect the chain to the flush lever with about ½ inch of slack, and trim any excess chain.
Universal flappers fit about 90% of toilets. If yours has an unusual flush valve, bring the old flapper to the store for an exact match.
Some newer toilets use canister-style flush valves instead of flappers. Check your model before buying parts.
Adjust the Float Level (If Water Overflows)
Step 4 of 6If water is flowing into the overflow tube, your float is set too high. For a ball float, bend the metal rod slightly downward or turn the adjustment screw. For a cup float (cylinder on the fill valve shaft), squeeze the clip and slide it down about half an inch. The water level should be about 1 inch below the top of the overflow tube.
Most overflow tubes have a water level line marked on them. Aim for that mark.
Replace the Fill Valve (If Still Running)
Step 5 of 6If the flapper and float are fine but water still runs, replace the fill valve. Disconnect the water supply line from the bottom of the tank (have a bucket ready). Unscrew the lock nut holding the fill valve, remove the old valve, and insert the new one. Hand-tighten the lock nut, reconnect the supply line, and attach the refill tube to the overflow pipe.
Do not overtighten the lock nut — you can crack the porcelain tank. Hand-tight plus a quarter turn with pliers is sufficient.
Test and Adjust
Step 6 of 6Turn the water supply back on slowly and let the tank fill. Watch for leaks at the supply connection and around the base of the fill valve. Flush two or three times to confirm the flapper seals properly and water stops at the correct level. Listen for silence — a properly working toilet is quiet between flushes.
If the new flapper still leaks, the flush valve seat may be corroded. You can smooth it with an emery cloth or replace the entire flush valve.
Recommended Products
The industry standard fill valve. Fits most toilets, easy to install, and comes with a refill tube and mounting hardware.
Adjustable universal flapper that fits most 2-inch flush valves. Features a built-in dial to control flush volume.
All-in-one kit with fill valve, flapper, flush valve seal, and tank-to-bowl hardware. Everything you need for a full toilet overhaul.
Essential for any plumbing job. Adjustable jaw grips nuts and supply lines securely without slipping.
Affiliate Disclosure: We earn a small commission when you buy through our links at no extra cost to you.
Tips & Warnings
- Buy a complete toilet repair kit for $15-$20 — it includes a flapper, fill valve, and all hardware, covering every possible cause.
- Take a photo of your toilet internals before you start so you remember how everything connects.
- Write your toilet model number down (stamped inside the tank or on the bowl) for exact part matches.
- Check the flapper chain length — too tight prevents sealing, too loose prevents a full flush.
- Always shut off the water supply before working inside the tank.
- Porcelain tank lids are heavy and break easily — set them on a towel on the floor, not on the toilet seat.
- If you see cracks in the tank or bowl, do not attempt repair — replace the toilet.
- If water is leaking from the base of the toilet (not the tank), the wax ring needs replacement, which is a separate project.
Frequently Asked Questions
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