Short answer
Make sure the shut-off valve behind the toilet is fully open. Lift the tank lid and check that the float moves freely and is not caught on the tank wall or the chain. If it still fills slowly, shut off the water, take the cap off the fill valve and flush out the grit. If nothing helps, replace the fill valve or call a plumber.
How to fix a toilet tank that will not fill
1The tank stays almost empty
After a flush it fills slowly or not at all. Lift the lid: here the float is stuck up, so the valve thinks the tank is full.
Read all the steps
- The tank stays almost empty. After a flush it fills slowly or not at all. Lift the lid: here the float is stuck up, so the valve thinks the tank is full.
- Open the shut-off valve all the way. Turn the valve behind the toilet counterclockwise until it stops. Someone may have closed it partway.
- Free the float. Move the float up and down by hand. If it rubs the tank wall or catches on the chain, nudge it free. The water should start to rise.
- Rinse grit out of the fill valve. Shut off the water, twist off the fill valve cap and hold a cup upside down over it. Open the valve for a few seconds: the burst flushes out grit.
- Cap on, water on, full tank. Put the cap back, open the valve and let the tank fill. It should stop about 1 inch below the top of the overflow tube.
- Still not fixed? Call a plumber Especially if: the shut-off valve is stuck or leaks, or water barely comes out of the supply line.
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Why it happens
- The shut-off valve is partly closed or clogged.
- The float is stuck or set too low.
- Grit or mineral buildup clogs the fill valve, often after work on the water main.
- The fill valve is worn out.
- The flapper leaks, so water runs out as fast as it comes in.
Replacing the fill valve
Universal fill valve kits at hardware stores fit most toilets. Shut off the water, flush, sponge out the rest of the tank and unscrew the supply line under the tank. Follow the kit to set the height and clip the small refill tube to the overflow tube. If the nut under the tank will not budge, call a plumber.
What not to do
- Do not force a stuck shut-off valve with pliers. Old valves can snap or start leaking.
- Do not bend the arm of an old ball float to make it fill. Use its adjustment screw.
When to call a plumber
- The shut-off valve is stuck or leaks, or water barely comes out of the supply line.
- Several faucets in the house also have low water pressure.
- The tank still fills slowly with a new fill valve.
- Water leaks under the tank after you replace a part.
Frequently asked questions
Why is my toilet tank not filling up?
Usually a partly closed shut-off valve, a stuck float or a fill valve clogged with grit. A leaking flapper can also drain the tank as fast as it fills.
How long should a toilet tank take to refill?
About a minute or less on most toilets. If yours takes several minutes, check the valve, the float and the fill valve.
How do I clean a toilet fill valve?
Shut off the water, remove the fill valve cap, hold a cup upside down over the valve and turn the water on for a few seconds. The burst flushes out the grit. Put the cap back and test.
Can low water pressure make a toilet fill slowly?
Yes. If every faucet in the house is weak too, the problem is the water supply, not the toilet. Call a plumber or your water utility.
Is it hard to replace a toilet fill valve?
Not usually. Universal kits come with instructions. If the supply nut is corroded or the shut-off valve does not close fully, let a plumber do it.