Fix a Toilet That Will Not Flush
Repair a toilet that will not flush by checking the handle, chain and fill valve. Replace worn parts to restore a full flush.
Quick answer
Take the lid off the cistern. Check whether the water level reaches the fill line. Check the chain is attached to the lever and the flapper valve. If the chain is broken or the flapper is warped, replace them. If the fill valve is faulty, turn off the water and install a new one.
A toilet that will not flush is usually caused by a disconnected chain, a warped flapper or a faulty fill valve. Most problems are visible once you lift the cistern lid. You can fix them with basic tools.
What you’ll need
- adjustable spanner
- replacement fill valve or flush mechanism (if needed)
- sponge and bucket
- cloth
- torch
Step by step
- 1
Inspect the cistern internals
Remove the cistern lid and place it on a towel. Shine a torch inside. Check the water level. It should sit about an inch below the overflow pipe. Look at the chain that links the flush handle to the flapper valve.
- 2
Reattach or adjust the chain
If the chain has come off the lever or the flapper, clip it back on. The chain should have a small amount of slack. If it is too tight, the flapper may not seal. If it is too loose, the lever cannot lift it.
- 3
Check and replace the flapper valve
Lift the flapper and feel the rubber seal. If it is warped, cracked or covered in limescale, it will not create a seal. Buy a matching replacement from a hardware shop. Unclip the old one and clip the new one in place.
- 4
Test the flush mechanism
Press the flush handle. The flapper should lift fully and stay up until most of the water drains. Then it should drop back into place and seal. If water keeps running, the seal is not seating properly.
- 5
Replace the fill valve if necessary
If the cistern does not refill after flushing, the fill valve may be blocked or broken. Turn off the water at the isolation valve behind the toilet. Flush to empty the cistern. Sponge out remaining water. Unscrew the old fill valve with an adjustable spanner and fit the new one.
- 6
Turn the water back on and test
Open the isolation valve slowly. Let the cistern fill. Check for leaks around the base of the new valve. Flush three times to confirm the toilet empties and refills correctly.
Turn off the water before replacing the fill valve. Place a bucket under the cistern when disconnecting pipes. Do not overtighten plastic nuts. They crack easily. If water leaks onto the floor, mop it up immediately to prevent slips and floor damage.
Common mistakes
- Overtightening plastic nuts on the fill valve, which causes cracks and leaks
- Not turning off the water before removing the old fill valve
- Buying the wrong replacement part. Take the old flapper or valve to the shop to match it
- Ignoring a running toilet, which wastes water and increases bills
Frequently asked
Why does my toilet keep running after I flush?
The flapper valve is probably not sealing against the flush valve seat. Clean the seat and check the flapper for warping. Replace it if necessary.
Can I fix a broken handle without tools?
Sometimes. If the nut inside the cistern has come loose, tighten it by hand. If the handle arm is snapped, you will need a replacement handle kit.
Do I need to drain the cistern to change the fill valve?
Yes. Turn off the water and flush to empty as much as possible. Sponge out the rest so you do not spill water when unscrewing the valve.
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