How to replace a toilet cistern

Most of us take our toilets for granted despite how crucial these fixtures are to our daily living. As toilets are used multiple times a day, unfortunately, they will need to be replaced eventually.

However, it isn’t always necessary to replace the whole toilet, you may just need a new cistern. That’s why learning how to replace a toilet cistern can be a great skill to acquire.

Today, we will look at the different stages involved in changing a cistern as well as the tools needed, how to fit a toilet cistern syphon, and how to fit a new toilet cistern.

Please note, if this isn’t exactly what you need, we also have guides on how to fit a toilet and how to fit a toilet pan to the floor.

Tools and materials needed

Whether you have reached the point where your toilet cistern no longer functions or you are pre-emptively changing it, this guide is perfect for you. First, you will need to gather the following tools and materials:

• Wrench
• Nuts and washers
• Spirit level
• Correctly sized relevant cistern (including flush)
• Sealant and sealant guns

How to replace a toilet cistern step-by-step

Once you are ready to begin, always start by isolating the existing water supply and turning it off. You can then flush the toilet to empty water from the cistern. If you have correctly switched off the supply, it won’t refill.

So, if you are unsure how to change a toilet cistern just follow the below step-by-step instructions:

1. Before jumping in headfirst, check your replacement cistern is the correct ordered size and specification before removing the old one.
2. It may also be a good idea to use a smartphone to take a photograph of how the cistern is connected, for future reference.
3. Now, start by undoing the inlet pipe at the base of the cistern.
4. Un-screw the cistern from the wall and any fixings.
5. Next, remove the cistern from the wall and the toilet pan.
6. You can then remove the new cistern from its box and follow the manufacturer’s instructions. It should be fairly obvious how things are connected and almost as simple as reversing your earlier steps.
7. Use a spirit level to check your new cistern is straight before re-fixing it to the wall.
8. Once fitted, turn on the water and wait for the cistern to fill with water.
9. Next, flush the toilet to check that all is working as it should.
10. Finally, seal the toilet to the floor with the sealant gun.
11. Please note, you may need to fit a new flushing mechanism.
12. Well done, you have learnt how to change a toilet cistern!

Top tip: Where water is involved, always have a bucket or old washing up bowl and towels to hand – just in case.

How to fit a toilet cistern

Fitting a new toilet cistern may be done as part of changing a whole toilet or on its own. It may also be done as part of a renovation, for cosmetic reasons, or it may be an essential change. Remember, the cistern is fundamental to the proper functioning of your toilet, otherwise, it is just a glorified bowl.

Ready to learn how to install a toilet cistern? You will need the below tools and materials:

• Wrench
• Nuts and washers
• Spirit level
• Correctly sized relevant cistern (including flush)
• Sealant and sealant guns
• Drill – such as a ‘Hilti’ type drill for drilling into tiles

Once you have gathered the above vital items, follow the below steps to discover how to install a toilet cistern:

1. Remove the new cistern from its box and review any manufacturer’s instructions.
2. Line up the new toilet cistern with your toilet pan and establish where the new cistern’s wall fitting holes are located.
3. Mark and drill any necessary holes into your wall.
4. Next, connect the new cistern to your toilet pan.
5. You can then attach the inlet pipe at the base of the cistern.
6. Remember to also connect the flush button at the top of the cistern.
7. Once everything has been properly fitted, turn on the water supply and wait for the cistern to fill back up again.
8. To check your new cistern is working correctly, flush the toilet.
9. Also, reseal the toilet base to the floor.
10. Finally, if a separate flush button is required, it may be an idea to do so whilst the cistern is away from the wall.

How to fit a toilet cistern syphon

Toilet syphons are an important component that allows your toilet to properly flush. A broken syphon can be a huge issue, particularly if you have guests staying with you. Therefore, knowing how to replace a toilet cistern syphon can come in handy time and again.

You will need:

• Pliers
• Screwdrivers
• A connection kit – This may be required if you are re-using an existing cistern where the seal may not re-fit as well as it previously did
• Syphon

Next, follow the below instructions:

1. To start with, remove the current cistern. Do this by using the instructions above in our ‘how to replace a toilet cistern’ section.
2. Once the cistern has been disconnected, remove the large nut from the bottom of the syphon.
3. Next, remove and clean around the area where you removed the syphon.
4. Slide the rubber washer that is usually included as part of the syphon kit over the threaded length.
5. You can then insert the new syphon into place.
6. Remember not to use silicone to re-seal.
7. Next, tighten the nut to the base of the syphon with pliers.
8. Place the doughnut washer, normally included, over the fixing plate.
9. Then place the cistern unit back onto the WC pan and re-connect the inlet.
10. Turn on water supply and once the cistern has re-filled, flush to check all is working as required.

Need more information on installing syphons? Please see our how to replace a toilet syphon guide.

Feeling confused?

While we have written this guide to hopefully make replacing a toilet cistern easier for you to do yourself this can still be a tricky project, especially for anyone new to the world of DIY. If you are struggling to follow along or are feeling confused, now is a good time to call in a professional.

Never be embarrassed to ask for help, that is the best way to learn after all. In fact, using our free search feature is a great way to connect with trusted tradespeople in your area. If you want to know more about professional toilet cistern fitting, please see our toilet installation cost guide.