Toilet Isn’t Flushing & How To Fix it

Low water level in the cistern

If your toilet isn’t flushing, the cistern is the first place to check. For a toilet to flush properly it needs a full tank of water to create enough force to clear the bowl. If the water level in the cistern is too low, the flush won’t be effective.

Open the cistern and check the water level. If there’s no marking, a good rule of thumb is that the water should be about 2.5cm (1 inch) below the overflow pipe (the vertical plastic pipe inside the cistern.) If it’s lower than that, you might have a faulty flapper valve, an issue with the fill valve or float or another problem stopping the flush mechanism from working correctly.

Low water level in the cistern: stuck float

Cause: The float (also known as the float valve or ballcock) controls the water level in the cistern. It’s the float height that determines when the cistern stops refilling, so if the float can’t move upwards, the cistern won’t refill to the correct level.

Fix: Give the float a wiggle to make sure it’s not stuck and is able to move freely.

Low water level in the cistern: incorrect float height

Cause: If the float is set too low, it won’t trigger the fill valve (also called a cistern inlet valve) to let more water into the cistern, so again, there won’t be enough water for a proper flush. 

Fix: Raise the float height:

• For a ball float: Bend the metal arm slightly upward. You should then see the water level rise. 

• For a plastic float cup: Turn the adjustment screw (often on top of the valve) to raise the water level.

If your float is looking old or worn, it might be a good idea to swap it out for a new float valve.

Low water level in the cistern: problem with the fill valve

Cause: The fill valve might be worn or partially blocked.

Fix: Inspect the valve and clean it (disassemble first), if it looks like it’s not in great shape. If there’s limescale buildup, soak the parts in a limescale remover. If the fill valve looks old or seems faulty you’ll need to replace it with a new fill and flush valve.

If you’ve found one of these problems and taken the right steps to fix it, let the cistern fill. Then test the flush to make sure everything’s working properly.

Low water pressure

Cause: Low water pressure can affect water levels in the cistern (and the speed at which the cistern refills).

Fix: Check for any problems with the water supply:

• Make sure the isolation valve (a small tap on the pipe that supplies water to the cistern) is fully open. If the valve is partially closed, it could prevent enough water going into the cistern.

• Check for kinks or blockages in the supply pipe that might be restricting the flow of water.

• Check other taps in the house. If pressure is low throughout the house, the problem isn’t confined to your toilet. We recommend calling in a qualified plumber to find and fix the problem. Choose one who’s registered with the CIPHE.

Leaking cistern

Cause: If there’s a leak from the cistern into the toilet bowl, it can mean the cistern never fully refills. The culprit is usually a faulty flush valve (the part at the bottom of the cistern that releases water into the bowl during flushing) or a worn-out washer or seal beneath the flush valve.

Fix:

• Add food colouring or a leak detection dye to the cistern. 

• Wait 15 minutes (don’t try to flush the toilet). If the water in the bowl changes colour, you’ve got a leak.

• Inspect the flush valve, washer and seal and replace them if needed.

Damaged flapper valve

If you’ve checked the cistern and the toilet is still not flushing properly, the flapper valve could be the problem. If water is draining from the cistern but isn’t entering the bowl with enough force, the toilet flapper valve might be damaged.

The flapper valve is the rubber plug at the base of the cistern. When you flush the toilet, it lifts to let water rush into the bowl. If it’s warped, cracked or not sealing properly, water will leak through, leaving the cistern half-empty and the flush too weak to do its job.

How to fix a toilet not flushing because of a damaged flapper valve:

1. Turn off the water supply. Empty the cistern by raising the flapper valve – you’ll see water drain into the bowl. (If this doesn’t happen, scoop out the water using a cup or jug.)

2. Inspect the flapper valve. Look for cracks, warping or wear. 

3. If something doesn’t look right, get a replacement fill and flush valve (they’re straightforward to fit).

4. Test the flush. Once you’ve installed the new flapper valve, refill the cistern and test it out.

Loose or broken flush button

Still wondering how to fix a toilet not flushing? A loose, broken or disconnected flush button can easily get you saying ‘my toilet won’t flush!’ in frustration. Follow these steps to find out if there’s a problem with your flush button or handle, and fix it.

How to fix a loose flush button:

• Tighten up connections inside the cistern. Take off the cistern lid. You’ll see that the flush button is connected to the flushing mechanism by a rod or small tube. If any parts seem loose or disconnected, reattach or adjust them so that all connections are tight and secure.

• Tighten the flush button. The button is held in place by a ring or nut under the cistern lid. If it feels wobbly, twist it to tighten it. You might not even need a tool to do this –  it’s something you can often do by hand.

• Replace the flush button. If the button is cracked or broken, you should fit a new toilet flush button. 

Blockages in the toilet or pipes

We’ve all experienced that sinking feeling when water starts rising quickly up the toilet bowl instead of draining away. That’s a sign of a blockage in the toilet or pipes (often because something that shouldn't be flushed down a toilet has been, such as wet wipes, sanitary products or too much paper). There are several ways to get your toilet flushing properly again.

How to fix a blocked toilet using a plunger: The toilet plunger is your first port of call. A good-quality plunger makes short work of most minor blockages. Place it over the toilet hole, press down firmly and pump several times to create suction.

How to fix a blocked toilet using a toilet auger: Toilet still not flushing? Your next stop is a drain auger, a flexible drain rod that can help break up more stubborn blockages. 

Don’t use chemicals to fix a blocked toilet. Chemical drain cleaners can damage pipes, especially in older systems. Avoid them if at all possible. There are lots of other drain cleaning tools to try first. If you’ve given these a go and your toilet’s still blocked, it’s time to step back and let a professional plumber handle it.