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?
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.
When Should You Replace Your Cistern?
Replacing a toilet cistern might be necessary under the following circumstances:
- Leaks: Persistent leaks can waste water and increase your utility bills.
- Cracks: Visible cracks in the tank can lead to structural instability.
- Malfunctioning components: Repeated issues with the flush mechanism, inlet valve, or float may indicate the need for a full replacement.
- Water inefficiency: Older cisterns may use more water per flush compared to newer, water-saving models.
- Aesthetic reasons: A dated or mismatched cistern can bring down the overall look of your bathroom, a new modern toilet cistern can refresh that look and be used to update your bathroom as part of a wider décor revamp.
Tools and Materials You’ll Need to Replace a Cistern
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:
- Adjustable spanner or wrench
- Screwdrivers (flat-head and Phillips)
- New toilet cistern (ensure it matches your current setup)
- PTFE/plumber’s tape
- Sponge and towel
- Bucket
- And plenty of patience!
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.
Step-by-Step Guide to Replacing a Toilet Cistern
Step 1: Turn Off the Water Supply
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.
Step 2: Disconnect the Old Cistern
Now for the messy bit:
- Unscrew the water inlet pipe underneath or at the side of the cistern.
- Undo the bolts or screws holding the cistern to the wall and/or toilet pan.
- Carefully lift the cistern away – there might be some leftover water, so have that towel handy again.
You might also need to remove any rubber washers, brackets, or sealant left behind.
Step 3: Prep the Area
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.
Step 4: Fit the New Cistern
Follow the manufacturer’s instructions for any internal fittings (like the flush and fill valves) – some cisterns come pre-assembled, others don’t.
Then:
- Position the cistern in place.
- Attach it securely to the pan and/or wall using the fixings provided.
- Reconnect the water inlet pipe using PTFE tape to help prevent leaks.
- Make sure everything is level and tight (but don’t overtighten!).
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.
Step 5: Turn the Water Back On & Test
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!
Tips for a Successful Replacement
- Measure before purchasing: Ensure the new cistern fits the dimensions of your toilet and bathroom space.
- Follow manufacturer instructions: Each cistern model has specific assembly and installation requirements.
- Inspect all seals: Check the condition of the rubber seals and washers before securing connections.
- Make sure that you do not overtighten: While secure connections are necessary, overtightening can damage components or create stress points or fractures.
- Seek professional help: If you’re unsure about any step, consider consulting a PM247 plumber to avoid costly mistakes.
Troubleshooting Common Issues
If something’s not quite right, here are a few things to look out for:
- Constant running water – You may need to adjust the float valve or check the flush valve seal.
- Leaks around the base – Double-check the seal between the cistern and toilet pan.
- Weak flush – Make sure the water level inside the cistern is high enough.
Benefits of Upgrading Your Toilet Cistern
Replacing your toilet cistern offers several advantages:
- Water conservation: Modern cisterns with dual-flush options can significantly reduce water usage.
- Improved look and feel: A new cistern can update and modernise the look of your bathroom.
- Efficiency: Replacing malfunctioning components ensures a smoother flush and reduces the likelihood of repairs.
- Environmental benefits: Saving water contributes to sustainable living practices and if you are on a meter saves you money too!
How Much Could a Leaky Cistern be Costing You?
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.
Not Feeling Confident? We’ve Got Your Back.
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.
Need a Hand? Contact PM247 Today
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.
Changing a Cistern FAQs
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.