A toilet cistern is the water tank you see behind or above your toilet bowl. It stores the water necessary for flushing. The cistern fills with water after each flush. Pressing the handle or button releases this water with force, flushing the toilet bowl.

How does this look? Check out the image below for a clear visual!

Diagram of a toilet

Where is the Cistern on a Toilet?

The cistern’s location depends on the type of toilet. There are two common configurations:

  • Close-coupled toilets: The cistern sits directly on top of the toilet bowl. This is a popular and space-saving design.
  • Back-to-wall toilets: The cistern hides within the wall behind the toilet bowl. Only the flush button or handle remains visible. This style creates a sleek, minimalist look.

How Does a Toilet Cistern Work?

A toilet cistern relies on a simple yet effective mechanism to flush your toilet. Here’s a step-by-step breakdown:

  1. Water storage: The cistern stores a specific amount of water, usually controlled by a float valve.
  2. Flushing action: Pressing the handle or button lifts the flush valve inside the cistern.
  3. Water release: Lifting the flush valve allows the stored water to rush down into the toilet bowl.
  4. Bowl cleaning: The force of the water flow effectively removes waste from the toilet bowl and pushes it down the drain.
  5. Refill: As the cistern empties, the float valve opens. The cistern refills to its designated level, ready for the next flush.

Should a Toilet Cistern Be Full of Water?

A toilet cistern should be filled with water, but not completely full. The correct water level is essential for the proper functioning of the toilet. Here are some key points:

  1. The cistern should be filled to a specific level, typically marked by a water line or determined by the float mechanism.
  2. The ideal water level is usually about 1 inch below the top of the overflow tube.
  3. This level ensures there’s enough water for a flush, preventing any weak flush problems, while also preventing overflow issues.

Can I Replace a Toilet Cistern Only?

Yes, while it is technically possible to replace only the cistern, there are some factors to consider:

  • Compatibility: Ensure the new cistern is compatible with your existing toilet bowl and configuration.
  • Skill level: The process involves several steps, including disconnecting the water supply, removing the old cistern, and installing the new one. If done incorrectly, this will result in a leak in your bathroom.
  • Tools required: You’ll need specific tools, such as an adjustable wrench, plumber’s tape, and potentially a new water inlet hose.

What are the Three Types of Toilets?

While the previous section explained how a cistern works, not all toilets are created equal. You’ll encounter different types, each with its advantages. Let’s break down the three main types:

1. Close-Coupled Toilets

  • Design: As mentioned earlier, the cistern sits directly on the toilet bowl in a close-coupled design.
  • Pros: Space-saving, affordable, readily available.
  • Cons: Can be harder to clean behind the cistern due to the tight space.

2. Back-to-Wall Toilets

  • Design: The cistern hides within the wall, offering a minimalist look.
  • Pros: Sleek aesthetics, easier to clean around the toilet area.
  • Cons: More expensive to install and may require more extensive plumbing work.

3. Wall-Hung Toilets

  • Design: Both the bowl and cistern are concealed within the wall. Only the flush plate remains visible.
  • Pros: Modern and minimalist appearance, maximises floor space, and is easy to clean.
  • Cons: It is the most expensive option; installation can be complex and requires a suitable wall structure.

What are the Disadvantages of a Cistern?

While toilet cisterns are the standard in many places, they do have a few drawbacks:

  • Potential for Leaks: The cistern’s various parts and connections can make it prone to leaks, which can lead to wasted water and potentially costly repairs.
  • Condensation: In humid environments, condensation can form on the cistern’s exterior. This can create a damp environment and potentially encourage mould growth.
  • Space Considerations: While close-coupled toilets offer a relatively compact design, back-to-wall and wall-hung toilets (especially those with concealed cisterns) require additional space within the wall cavity.
  • Noise: The filling mechanism of some cisterns can be quite noisy, especially older models which can also be prone to issues like the cistern not filling up properly.

However, it’s important to note that modern cisterns often incorporate features to minimise these issues. For example, dual-flush cisterns offer water-saving options, and newer models tend to have quieter filling mechanisms.

The advantages of a cistern, such as efficient waste removal and ease of use, often outweigh these disadvantages for most users.

Can You Have a Toilet Without a Cistern?

Yes, it is possible to have a toilet without a traditional cistern. There are several types of toilets that operate without a conventional cistern:

Tankless Toilets

Tankless toilets, also known as flushometer toilets, are commonly found in commercial settings but are becoming more popular in residential applications. These toilets:

  • Connect directly to the water supply line
  • Use water pressure to flush waste effectively
  • Eliminate the need for a storage tank or cistern

Macerating Toilets

Macerating toilets are another option that doesn’t require a traditional cistern:

  • They use a grinding or blending mechanism to liquefy waste
  • The waste is then pumped out through a small-diameter pipe
  • This system allows for toilet installation in areas where conventional plumbing is not feasible

Composting Toilets

Composting toilets are an eco-friendly alternative that doesn’t use water or a cistern:

  • They separate liquid and solid waste
  • Solid waste is broken down through natural decomposition
  • These toilets are often used in off-grid or environmentally conscious settings

Wall-Hung Toilets with Concealed Cisterns

As mentioned earlier, while these toilets do have cisterns, they are hidden from view:

  • The cistern is installed behind the wall
  • Only the toilet bowl is visible, creating a sleek, modern look
  • This design saves space and is easier to clean around

Do You Need a Plumber To Install a Toilet Cistern in Australia?

Yes, in most cases, you need a licensed plumber to install or replace a toilet cistern in Australia. This is because:

  1. According to the Australian Plumbing Code, plumbing work involving sewer or drinking water must be carried out by a qualified plumber.
  2. Regulations vary by state, but generally, a plumber’s license is required for any significant plumbing work beyond minor repairs.

It is illegal in most situations for unlicensed individuals to conduct DIY plumbing work like replacing a cistern. This is because:

  1. DIY jobs often don’t comply with strict Australian standards.
  2. There are legal issues and safety concerns with unlicensed plumbing work.

While some minor toilet repairs can be done DIY, replacing the entire cistern is typically not allowed. You may be permitted to:

  • Replace washers, float valves, and other small internal components.
  • Repair leaking taps or replace showerheads.

Hiring a licensed plumber for cistern replacement provides benefits like:

  • Ensuring the work is done safely and correctly.
  • Avoiding potential legal consequences or insurance issues.
  • Having expertise to handle any unexpected challenges.