How to fix a toilet flush - how to repair a slow flushing toilet yourself

Want to know how to fix a toilet flush? Repair a toilet that won’t flush quickly and efficiently in seven simple steps

white bathroom with pattern tiles
(Image credit: Future PLC/Lizzie Orme)

Knowing how to fix a toilet flush is one of those DIY that could save you money and time. In order to fix a toilet flush, you firstly need to understand its construction and how it works. This can also help when understanding how to unblock a toilet.

A toilet flush consists of two separate and independent components. The first of these is the filling mechanism which is made up of a shut off valve and a float valve. The shut-off valve controls the flow of water entering the toilet system and the float valve controls the level of water that enters the cistern. It then shuts off when the required level of water has been reached.

The second component is the flushing mechanism, which is made up of the flush control (the handle or button you push to release the flush of water), the flushing plug (also known as a flapper) and the overflow. The flapper is usually a small rubber stopper in the bottom of the toilet’s cistern that flaps up and down as and when you use the flush control to prevent water from flowing into the bowl when the flush is not in use. The overflow directs excess water into your toilet pan to prevent a bathroom flood in the event of a malfunction. 

How to fix a toilet flush

white toilet in grey tiled bathroom

(Image credit: Tap Warehouse)

‘You’ll notice when the flush is broken because your toilet won’t flush and/or the flush will be limited and won’t operate correctly,’ says Rikki Fothergill at Big Bathroom Shop.

‘This means that the waste in the toilet will gather, and it could prevent you from being able to use the toilet at all,’ says Matthew Jenkins at MyJobQuote. ‘And, if you leave the waste in the toilet bowl, this can start to smell and could cause staining or further damage to the toilet bowl.’ 

 That is certainly the last thing you want impacting your bathroom ideas. So we've devised a guide to help you find the cause and the solution to fixing the toilet flush. Remember to always seek professional help if you don’t feel comfortable carrying out the job yourself.

1. Understand what causes a toilet flush to break

There are several issues that can cause a toilet flush to break. ‘There might be a blockage, the water level could be incorrect, the handle or button mechanism could be faulty or you might have a problem with the flush valve,’ says Steven Pester of Resolve Plumbing Services LTD at Rated People.

2. Adjust the water level

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(Image credit: Bathroom Mountain)

If the water level isn’t correct, the toilet won’t be able to flush because not enough water can be dumped into the bowl. ‘The water level needs to be a minimum of 3cm beneath the overflow tube of the tank,’ explains Steven Pester. 

Like how to fix a running toilet, it’s usually an easy fix. ‘Often, it’s as simple as twisting the flush valve until the water reaches the optimum level,’ says Matthew Jenkins. ‘In other cases, the float ball may not have been adjusted appropriately, making it sink too low which signals that the tank is full before it actually is. In which case, the ball simply needs to be adjusted in height.’

3. Replace a faulty toilet handle

A broken flush handle is likely caused by it being fitted too loose or too tight, both of which prevent the flush mechanism from working properly. 

‘Try tightening or loosening the mounting nut at the back of the handle and check for a limescale build-up which could be preventing the handle’s movement,’ says Rikki Fothergill. ‘If all else fails, take the old broken flush handle to the DIY store and get them to supply an identical replacement – most flushes are pretty standard, so you shouldn’t have any issues finding the correct part.’ 

4. Install a new toilet flush

toilet flush handle on white toilet

(Image credit: Rufus Stone / Alamy Stock Photo)

‘If, when you flush the toilet, you do not hear running water filling the tank, it’s likely that the issue lies with the filling mechanism,’ says Rikki Fothergill. Which will mean replacing the toilet flush valves. ‘Always follow manufacturer instructions on how to remove the old valves and install new ones correctly.’

5. Insert a new flush mechanism

If no water pours into the bowl after pushing the handle, it could be that the lift chain attached to the top of the flapper and the flush handle has broken. If the flapper is damaged, possibly because it has corroded over time, it can cause water to constantly fill the bowl. The solution is to replace both. 

Make sure you know the make and model of your toilet before purchasing a new flapper and lift chain to ensure you replace them with the correct factory parts. 

6. Unclog the toilet

white bathroom with pattern tiles

(Image credit: Future PLC/Lizzie Orme)

Your toilet might not be flushing due to a blockage. Using too much toilet paper, or throwing sanitary products, face wipes and other items down the toilet can cause it to clog. 

Try pouring hot water down the toilet bowl and then flushing after a few minutes. If that doesn’t fix it, try plunging a few times. If this still doesn’t work, you will need to call in a plumber who has specialist tools to unclog toilets. It's worth having your own home essential tools.

7. Sort out a drain line problem

If the toilet appears to be working correctly but still won’t flush, there might be an issue with your home’s plumbing. 

‘The drain lines move your waste to your sewer. If you notice the other drains in your house aren’t working such as your sinks, bathtub, and shower, it could be that the drain line is clogged or broken,’ says Matthew Jenkins. 

‘Unfortunately this isn’t a DIY job and will require the help of a professional plumber to come and unblock it. You will likely need to organise a CCTV drain survey as well to determine the cause of the drain line issue before any work is carried out.’

How much does a plumber typically charge per hour to fix a toilet flush? 

If you need to call the experts in, Steven Pester of Resolve Plumbing Services LTD at Rated People suggests budgeting from £80 per hour (plus parts) to fix a toilet flush. 

Sophie Vening

Sophie Vening is a freelance journalist and editor with more than 16 years’ experience writing about homes and properties. She’s worked for some of the UK’s leading interiors, self-build and property titles including, Grand Designs, Ideal Home, House Beautiful, Build It, The Metro Homes & Property and The Evening Standard Homes & Property. 

She enjoys writing about complex issues in an easy-to-understand way.