How to Replace a Toilet Cistern

toilet cistern

Dealing with leaking toilet cisterns can be both frustrating and inconvenient. Not only does it waste water, it can also lead to a wet floor and potential damage to your bathroom. In such cases, replacing the faulty toilet cistern becomes necessary to restore the proper functioning of your toilet.

Whether you’re a seasoned DIY enthusiast or a beginner in plumbing system repairs, this comprehensive guide will walk you through the step-by-step process of replacing toilet cisterns, ensuring a leak-free and fully functional bathroom.

What are Toilet Cisterns and Their Components?

toilet repaire

Toilet cisterns, or toilet tanks, are containers at the back of the toilet bowl holding water for flushing. It plays a vital role in the functioning of the toilet by storing and releasing water during the flushing process.

The components of typical toilet cisterns include:

  • Inlet Valve: The inlet valve, also known as the fill valve or ballcock, controls water flow into the cistern. It is connected to the water supply line and opens to allow water to enter the cistern when the water level drops.
  • Float Valve: The float valve, often called the ball float or float ball, is connected to the inlet valve. It rises with the water level in the cistern and shuts off the inlet valve when the desired water level is reached, preventing overfilling.
  • Flush Pipe: The flush pipe is a tube that connects the cistern to the toilet bowl. It allows water to flow from the cistern into the bowl during flushing.
  • Outlet Valve: The outlet valve, also known as the flush valve or flapper valve, is located at the bottom of the cistern and controls the release of water into the toilet bowl during flushing. It opens when the flush button or lever is pressed and closes to stop the water flow.
  • Rubber Seal: The rubber seal, the flush valve seal or flapper, is attached to the outlet valve. It forms a watertight seal when the valve is closed, preventing water from continuously flowing into the toilet bowl.

These components work together to ensure the proper functioning of toilet cisterns. When the flush button or lever is pressed, the inlet valve opens, allowing water to flow into the cistern. The float valve rises with the water level and shuts off the inlet and overflow valve once the desired water level is reached. When the flush button or lever is released, the outlet valve opens, and water flows from the cistern into the toilet bowl, creating a flush.

Understanding these components is essential when troubleshooting and replacing faulty parts that may cause drainage problems or a leaking or malfunctioning cistern.

5 Steps in Replacing Toilet Cisterns


When dealing with a leaking toilet cistern, the steps for replacement can vary depending on the specific situation. Here are five general steps to consider when replacing leaking toilet cisterns, considering the unique circumstances that can influence the process.

Step 1: Preparation and Safety Measures

Before replacing the toilet cistern, turn off the water supply to the toilet. Locate the water valve near the toilet’s base and turn it clockwise to shut off the water flow. Ensuring the water supply is entirely closed is crucial to prevent potential leaks during the replacement process.

Additionally, placing towels or a bucket on the floor around the opening of the toilet can help catch any water that may spill.

Step 2: Remove the Old Cistern

To begin the replacement process, remove the lid of the toilet cistern by gently lifting it. Place the lid in a safe area where it won’t get damaged. Next, disconnect the water supply hose from the bottom of the toilet pan and the cistern. Use an adjustable wrench to loosen the nuts and carefully remove the hose.

Now, locate the fixing bolts that secure the cistern to the wall. These bolts can usually be found at the bottom or back of the concealed cisterns. Unscrew the nuts on both bolts and set them aside. Gently lift the cistern straight up to detach it from the wall brackets. Be cautious, as the cistern may still have some water, which could spill during removal.

Step 3: Install the New Cistern

Once the old cistern is removed, it’s time to install the new one. Start by attaching the wall brackets to the back of the new two cisterns, following the manufacturer’s instructions. Ensure that the brackets are securely fastened.

Carefully position the new cistern onto the wall, aligning the fixing bolts with the holes on the cistern brackets. Insert the bolts through the holes and tighten the nuts by hand. Use a wrench to secure them firmly, but avoid overtightening, as it may damage the cistern or the toilet bowl.

Step 4: Reconnect the Water Supply

Now that the drainage system for the new cistern is in place, it’s time to reconnect the water supply. Attach the water supply hose to the bottom of the cistern, securing it tightly with the wrench. Ensure the connection is leak-free by testing it with a small amount of water.

Step 5: Test for Leaks and Functionality

With the new cistern installed and the water supply reconnected, testing for leaks and ensuring proper functionality is important. Slowly turn on the water valve to allow water to fill the cistern. Monitor the connection points and the cistern base for any signs of leakage. If you notice any leaks, tighten the connections or replace faulty parts, such as washers or seals.

Once the cistern is filled with enough water, check the flushing mechanism by pressing the flush button or lever. Ensure that the water flushes properly into the water line of the toilet bowl and that the float valve operates correctly to stop the water flow once the cistern is full.

Remember, replacing a leaking toilet cistern depends on the specific circumstances and the extent of the damage. If you’re unsure or encounter any complications, it’s recommended to consult a professional plumber who can provide expert guidance and assistance tailored to your situation.

Toilet Cistern Leaking? When to Call a Professional

While replacing toilet cisterns can be a manageable task for some homeowners, there are situations where it is best to call a professional plumber, especially when dealing with a leaking toilet cistern. Here are some instances when seeking the expertise of a plumber is recommended:

  • Persistent or Severe Leaks
  • Complex Plumbing Systems
  • Lack of Plumbing Experience
  • Time Constraints
  • Warranty or Insurance Coverage

Remember, a leaking toilet cistern can lead to water wastage, higher utility bills, and potential damage to your bathroom. If you’re unsure about tackling the replacement yourself or if the leak is persistent or severe, it’s always best to call a professional plumber. They have the expertise and tools to diagnose and resolve the issue effectively, ensuring a leak-free and properly functioning toilet cistern.

Final Thoughts

Replacing a toilet cistern may seem daunting, but with the proper guidance and tools, it can be a manageable DIY project. However, it’s essential to recognise your limitations and know when it’s best to call a professional plumber for assistance. If you encounter complex plumbing systems, persistent leaks, lack of plumbing experience, time constraints, or if your cistern is under warranty or insurance coverage, seeking the expertise of a plumber is recommended.

Don’t let a small leak turn into a larger problem. With the right approach and the necessary knowledge, you can resolve the issue and restore your toilet to its optimal condition.

Please note: This information is provided for advice purposes only. Regulations differ from state to state, so please consult your local authorities or an industry professional before proceeding with any work. See our Terms & Conditions here.

Last Edited on: 18th September 2023

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