12 June 2025
If your toilet cistern has seen better days – maybe it’s cracked, leaking, or simply not doing its job – you might be considering replacing it. The good news? It’s not as daunting as it sounds. With a bit of patience and the right tools, many people can manage this job themselves.
At PM247, we’re always here to help. But if you’re handy with a spanner and fancy giving it a go, we’ve put together this straightforward step-by-step guide. And of course, if anything goes wrong (or you’d rather leave it to a pro), our expert plumbers are on standby 24/7. Before get into the guide, let’s start with the very basics. What is a toilet cistern?
A toilet cistern is the tank located at the back of a toilet that holds water for flushing. When you press the flush lever or button, the cistern releases water into the toilet bowl to clear waste. It operates using a combination of a float mechanism, inlet valve, and flush valve to regulate water flow and refill the tank after flushing.
Replacing a toilet cistern might be necessary under the following circumstances:
Get yourself organised before starting any major jobs, there is nothing worse than getting into a project and then realising that you haven’t got the right part or tool to complete it. Here’s a list of tools and materials you’ll want to have on hand:
PM247 Tip: There are different types of cisterns – close-coupled, low-level, high-level, etc. Make sure you get one that’s compatible with your existing toilet pan.
Start by locating the isolation valve, usually found on the pipe leading into the cistern. Turn it clockwise until the water stops.
Flush the toilet to empty the cistern. There’ll still be a bit of water left inside – use your sponge and bucket to soak that up.
Now for the messy bit:
You might also need to remove any rubber washers, brackets, or sealant left behind.
Clean the top of the toilet pan and surrounding area. Scrape away any old sealant or grime to give your new cistern a good, clean surface to sit on.
Follow the manufacturer’s instructions for any internal fittings (like the flush and fill valves) – some cisterns come pre-assembled, others don’t.
Then:
PM247 Top Tip: What is PTFE Tape? PTFE tape, also known as plumber’s tape, is a thin film of polytetrafluoroethylene, hence the ‘PTFE’. It is used as a sealant and lubricant for threaded connections in plumbing and piping. It’s primarily used in piping systems to prevent leaks by filling gaps in threaded joints – providing a tight and waterproof seal.
Turn the isolation valve anti-clockwise to let the water flow back in.
Let the cistern fill, then give it a few test flushes. Check for leaks at all connection points. If you spot a drip, turn off the water and tighten the fittings again.
If all’s well, tidy up and job done!
If something’s not quite right, here are a few things to look out for:
Replacing your toilet cistern offers several advantages:
A typical leaking cistern (often due to a worn flush valve or faulty fill mechanism) can waste:
Between 200 and 400 litres of water per day – that’s 6,000 to 12,000 litres per month!
… Or up to 146,000 litres per year! That’s a lot of water.
According to the latest UK average water and sewerage charges (2024/25), the cost per cubic metre (1,000 litres) is roughly:
£4.34 per 1,000 litres (including water supply and sewerage charges – yes you have to pay to get rid of it as well!)
So:
200 litres/day = £0.87/day → ~£318/year
400 litres/day = £1.74/day → ~£636/year
Even a small toilet leak could be costing you between £300–£600+ a year in wasted water, enough water to fill a swimming pool each year.
Note: Some severe leaks (especially silent ones) can waste even more – up to 800 litres a day in extreme cases.
We know plumbing tasks aren’t everyone’s cup of tea. And while changing a cistern is very doable for confident DIYers, things don’t always go to plan. If you’re unsure at any point – or just don’t fancy the hassle – give PM247 a call.
Our experienced plumbers are available 24/7, ready to help with everything from a quick fix to a full installation. No stress, no mess – just reliable, professional service when you need it. Here’s what our customers say about our plumbing services.
Whether your cistern’s on its last legs or you’ve just decided DIY isn’t for you after all – don’t worry. Get in touch with our team for fast, friendly help.
Need a plumber to fix replace your toilet cistern? Call us on 08082 504 203 or fill in the form here to get your cistern replaced with a local PM247 plumber.
Can you change a cistern yourself?
Yes, if you are a confident (and skilled) DIY’er you can change a cistern yourself, the guide above will show you how, but if you have any doubts about your competency as home fixer perhaps it would be better to call in the professionals.
Can you just replace a cistern on a toilet?
Yes you can replace a cistern on a toilet, separately from the toilet bowl. If you would like to change the look and feel of your toilet, have a faulty cistern or just fancy a change then you do not need to buy and replace the entire bowl and seat, the cistern can be replaced independently.
Can you use any cistern with a toilet?
No you cant. Toilet cisterns are not standard sized and while there are some similar sizes and dimensions, they usually vary by type (close-coupled or concealed cisterns) and also by manufacturer.
Get a PM247 plumber to fix replace your toilet cistern. Call us on 08082 504 203 or fill in the form here.
