Not sure what a toilet cistern is or how it works? This guide will tell you everything you need to know about toilet cisterns and how they work.

Although it is one of the most used and important items in the home, most people do not pay much attention to toilets and cisterns.

When problems arise with these devices, such as a leak, it is important to understand them. Knowledge of toilet cisterns can be beneficial in various situations and help you troubleshoot problems effectively.

This guide will help you learn everything you need to know about toilet cisterns in the best possible way. So without further ado, let’s get down to business.


Standard household toilets usually consist of several components, including the bowl and the cistern. The cistern, generally located at the top of the system, is the element that stores the water used to flush the toilet. It is also commonly referred to as a reservoir.

The cistern is located near the bowl of modern toilets, which is called direct coupling. Previously, the tank was placed high above the toilet bowl and connected by a pipe. Another option was to hide the cistern in cupboards, on the wall or on the ceiling.

All cisterns have a flush pipe mechanism attached or locked to the tank body. This can be a lever or push button that releases water from the tank into the toilet bowl when pulled or pushed.


Three common toilet cistern parts are responsible for filling the cistern with water: a fill valve, a water supply line, and a float mechanism. The cistern base is connected to the supply line, allowing the plumbing system’s water to fill the tank.

The fill valve allows the water from the supply line to enter the storage tank while it is open. In turn, the float mechanism controls the valve, which registers the water level inside the tank.

The plastic float allows the fill valve to open or close based on the level of water present in the cistern. It opens the valve when the water level in the tank becomes too low and requires refilling.


Water enters the toilet bowl through the flush tank either by gravity or air pressure to flush the toilet. The user activates the flush by pressing the button or pulling the lever, while industrial and commercial toilets are mostly hands-free.

Sometimes a motion sensor to activate the flush is a hands-free option for industrial and commercial toilets. The float mechanism in the tank lowers after flushing the toilet, informing the fill valve that there is no water in the tank.

The float mechanism opens the valve and draws water from the supply line to fill the tank, ready for later use.

Various toilets are equipped with flushing systems ranging from a simple flush button to a half-tank flush. The latter is a low-flow flush for a liquid flush.

Flush systems cause significant water wastage, but dual flush systems are gaining popularity as they are far more efficient. You only use 4.5 liters of water per flush.

Dual flush tanks feature a two-button system, where a single button only empties the tank halfway, which is suitable for liquid waste. The other button opens the tank completely and is intended for solid waste.

FAQs about Toilet Cisterns

What is a toilet cistern?

A toilet cistern is the tank that stores water for the toilet to flush. It is typically located behind the toilet bowl and is connected to the toilet by a pipe.

Why do toilets need a cistern?

Toilets need a cistern to store water so that the toilet can flush without having to rely on a constant flow of water from the mains. This helps to conserve water and also makes the toilet more efficient.

What are the different types of toilet cisterns?

There are two main types of toilet cisterns: gravity-fed cisterns and pressure-assisted cisterns.

  • Gravity-fed cisterns: These cisterns use the force of gravity to flush the toilet. The water in the cistern is stored above the toilet bowl and is released when the flush valve is opened.
  • Pressure-assisted cisterns: These cisterns use a pump to pressurize the water in the cistern. This allows the toilet to flush more forcefully and efficiently.

What are the advantages and disadvantages of each type of toilet cistern?

  • Gravity-fed cisterns are simpler and less expensive than pressure-assisted cisterns. However, they may not flush as forcefully and may require more frequent maintenance.
  • Pressure-assisted cisterns are more expensive than gravity-fed cisterns, but they flush more forcefully and efficiently. They may also require less maintenance.

How do I know which type of toilet cistern is right for me?

The best type of toilet cistern for you will depend on your individual needs and preferences. Consider the following factors when making your decision:

  • Your budget: Gravity-fed cisterns are typically less expensive than pressure-assisted cisterns.
  • Your water pressure: If you have low water pressure, a pressure-assisted cistern may be a better option.
  • Your needs: If you have a large family or if you use your toilet frequently, a pressure-assisted cistern may be a better option.


Maintaining a modern toilet becomes much easier when you understand how a toilet cistern works. Despite the advancement and development of technologies, the standard tank system has remained more or less the same over the centuries.

While there aren't any major changes to how the tanks work, learning how they work is an effective way to be prepared for any problems that may arise.

This is a great benefit in situations where your toilet may need repairs, and helps reduce dependency on others while saving time and money. However, for serious problems, you may need to call a professional plumber in Jacksonville, Texas.