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How to replace a toilet cistern

person trying to fix the toilet - toilet cistern

From toddlers to teenagers, to full-grown adults, your toilet gets a lot of bums on seats (and therefore wear and tear). Eventually, you’ll want to replace your toilet – either because it’s getting worn out or you want to change up the decor in the bathroom.

However, you can always replace parts of your toilet in stages. This could be to keep a renovation within budget or perhaps a localised repair will do the trick for you. In this case, outside of a flusher, syphon or seat, your cistern might just be the part you replace. This guide will show you how changing a toilet cistern is simpler than you think. We’ll explain what a toilet cistern is, what it does and how it works so you can be matching up your colour swatches in no time.

Alternatively, go here if your toilet won’t flush, or if you need help unblocking a blocked toilet.

Table of contents

  1. What is a toilet cistern?
  2. How does a toilet cistern work?
  3. When should I replace my toilet cistern?
  4. Why is my toilet cistern leaking?
  5. How to replace a toilet cistern
  6. Replacing a toilet cistern FAQs

What is a toilet cistern?

The cistern is the top part of the toilet that holds the water (it’s sometimes known as the toilet ‘tank’), and it’s an integral part of the whole system. When you flush, the parts inside the cistern push that water held in the cistern down into the bowl of the toilet, which flushes it out down the waste pipe. The cistern then refills the bowl with clean water.

Different types of cisterns

You can get a few different types of cisterns, including:

  • Close-coupled cisterns:

You see these in most UK homes. The toilet looks like it’s in one piece, with the cistern attached to it just above the bowl.

  • Low-level cisterns:

This is a style of cistern for modern bathrooms. These cisterns are fixed just above the toilet bowl but with more of a sizable gap and a pipe running between them.

  • High-level cisterns:

This style of cistern looks at home in traditional bathrooms. The cistern is fixed high up on your wall, way above the bowl, and the pull lever is on a long chain. You see these a lot in old schools, restaurants and hotels.

  • Hidden cisterns:

These have been popular in recent years. They help to free up space so are ideal for small bathrooms, en-suites, or even for the elderly who have trouble getting down onto the loo.

How does a toilet cistern work?

Toilet cisterns are filled via a direct water supply pipe. This water supply is controlled by a valve, which is controlled by the plastic float you see floating on the water inside the cistern when you take off the lid.

The plastic float monitors the water level inside the cistern. On the other end, it opens and shuts the valve when it senses it’s necessary to fill the cistern to keep the water at the correct level. When you flush the toilet, the float senses there’s no water in the cistern, opens the valve, and allows water to enter.

When should I replace my toilet cistern?

Two reasons: changing styles or if there’s a fault.

What problems or symptoms do toilet cisterns develop?

You can get big problems caused by accidents or mishaps – or issues due to neglect or lack of maintenance.

  • Your toilet keeps running – a certain amount of water is constantly running into the bowl
  • Your toilet won’t flush
  • There could be a leak if you find that your cistern keeps filling with water
  • The cistern itself or its valves and mechanisms may have been damaged.

Why is my toilet cistern leaking?

There are quite a few moving parts inside a toilet cistern and they do get old or break. You can sometimes replace individual parts, but if there’s something wrong with the cistern itself – ie. it has been damaged, broken or cracked, there could be leaks. If there are serious leaks, you may be losing water (which will be costing you more than it should).

If your toilet cistern isn’t working as well as it did before, troubleshoot the following:

  • Is the toilet cistern leaking due to a crack or other damage?
  • Is the toilet not flushing (do you need to replace the syphon, for example)?
  • Is the toilet constantly running?
  • Is the toilet blocked?

Check out any of these plumbing problems first to make sure that replacing your toilet cistern is the last resort you need. If you’re 100% sure you need to replace your cistern, let’s do it.

How to replace a toilet cistern

DIY or plumbing newbie? Don’t worry. Replacing a toilet cistern is a suitable job for a beginner with some basic tools.

If you’re doubting you have the skills, call a professional and because it’s a super-simple job for them, they’ll sort it out in no time. If you’re prone to trying to white-knuckle these tasks yourself but getting it wrong or spending ages, it could end up costing you even more.

1. Get ready

Gather all the things you need:

  • Choose your new cistern! Aesthetics matter, so get the cistern that you prefer looks-wise, as well as its suitability with your existing set-up. You can get cisterns that are ceramic or plastic.
  • Plumbing tape
  • Adjustable spanner
  • Old towel (you always need an old towel with these types of jobs to mop up any spills)

Switch off the water supply

This can be at either the isolation valve close to the cistern, or at your mains water supply (warn the other members of your household if you’re going to do this).

Get rid of any water left in the cistern

Now flush the toilet until the cistern is empty. If you switched off the water successfully, the cistern will not refill. Now wipe your cistern down inside before you start removing it.

2. Remove your old cistern

Unscrew the water inlet pipe

Unscrew the water inlet pipe at the bottom of the toilet cistern – be warned it may still have water in it!

Unbolt the fixing screws

Use your adjustable spanner to unscrew the nuts and bolts holding the cistern onto the toilet bowl. Some of these may be plastic and some metal. Take a look at the washers as you do this – they may need changing too. Reach into the cistern to remove the bolts once the nuts are off.

Physically lift the old cistern off the bowl

You might need a little help to do this safely and get it out of the way.

3. Putting in the replacement toilet cistern

Retrace your steps in reverse

Line up the new cistern right where the old one sat. Make sure the washers and gaskets line up. You might need a friend to help hold it.

Screw it all back in

Take your plumber’s tape and wrap the inlet hose. Now place the water inlet hose back. Check everything is gently tightened and in the right position, including the washers.

Turn on the water again

Water should quickly fill the new cistern. Flush it a few times to test it’s all watertight.

Enjoy your new cistern!

Whether you replaced your cistern for aesthetic or functional reasons, you won’t have to worry about it again for a while. To give home renovators, homeowners and landlords extra peace of mind, our popular Plumbing and Drainage cover helps you plan for those unexpected mishaps. Take a look at our repair service too and our team will be happy to help.

Replacing a toilet cistern FAQs

Can you replace the cistern on a toilet?

Yes, it’s perfectly simple to replace a toilet cistern with a few tools and a strong pair of hands (or two).

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