Top 5 Reasons You Might Find Your Toilet Cistern Leaking

You walk into the bathroom and there’s a drip, a puddle on the floor or water running when the toilet hasn’t been flushed. If that sounds like you, chances are you've likely found your toilet cistern leaking.

Just like a leak from your hot water system, a leaking toilet cistern is more than a mere annoyance. It wastes water, increases your water bill, causes potential water damage and can even drive up repair expenses if you let it go for too long.

There are many common causes of a leaking cistern, from worn-out parts like the rubber seal to issues with the inlet valve or flush mechanism. Knowing the cause will help you fix a leaking toilet cistern and avoid more headaches. Let’s get into the common culprits.

Understanding the Parts of a Toilet Cistern

Knowing how to fix a leaking toilet cistern depends largely on understanding how the parts work together to make the toilet flush properly. Here’s a quick rundown of the key parts inside a cistern when you open the tank lid:

• Inlet valve: Controls the water flow into the cistern and the water level. You might also know it as the fill valve.
• Float valve: Works with the inlet valve to stop the flow from the water line when the cistern is full.
• Flush valve: Part of your cistern’s drainage system. It releases water from the cistern into the toilet bowl when you flush. Also known as the outlet valve.
• Flapper valve: Forms a watertight seal and lifts when you flush, allowing water to flow out.
• Overflow tube: Stops the cistern from overflowing by directing excess water into the bowl.

Now you know what the parts are, you’ll have a better idea of what might be the reason behind your toilet cistern leaking and how to fix it.

Reason 1: Worn Out Rubber Seal or Washer

A worn-out rubber seal or washer is one of the most common causes of a leaking cistern. Over time, these parts can wear out due to age, natural wear and tear, or exposure to water and cleaning chemicals.

The watertight seal between the cistern and the toilet bowl gets compromised when this happens, leaving you with drips or a wet floor around the toilet. You might also notice water pooling near the flush pipe seal or hear a faint hissing sound as water escapes.

Replacing the old seal with a new washer or seal is usually a fairly easy fix. But ignoring the issue will waste water and increase your water bill so it’s best to act fast.

Reason 2: A Faulty Inlet Valve or Float Valve

A faulty inlet valve or float valve can cause your cistern to leak, often in obvious ways.

The inlet valve controls the water flow into the cistern, while the float valve monitors the water level. If either of these parts fails, the cistern will overfill and water will spill into the overflow tube. You might see a constant trickle of water into the toilet bowl, a running sound or higher water bills.

Over time, normal wear and tear or excessive pressure in the system can cause these issues. Replacing or adjusting the faulty part will get the flush mechanism working again. You’ll stop the water leaks and save yourself some money and hassle in the process.

Reason 3: A Cracked Flush Pipe or Tank

A crack in the flush pipe seal or cistern tank can cause persistent annoying and damaging leaks. These cracks can occur for numerous reasons, often due to:

• age
• wear and tear
• accidental impact

They can often compromise the watertight seal required for the system to work properly.

If the flush pipe is damaged, water will escape and pool on the floor around your toilet. Cracks in the tank will cause a slow but steady loss of cistern water. They’ll leave you needing to refill the cistern more often.

Reason 4: A Faulty Flush Valve or Flapper Valve

A faulty flush valve or flapper valve is another common cause of a leaking cistern, often resulting in a running toilet.

As you press the flush button, the flush valve releases water from the cistern into the toilet bowl. Meanwhile, the flapper valve forms a watertight seal as the cistern refills. Damage or wear to either part will cause water to leak into the bowl. Symptoms are the sound of water running or trickling even when the toilet hasn’t been flushed.

A faulty flush valve seal or an improperly seated flapper valve are common reasons why you might find your toilet cistern leaking. Replacing these parts will likely stop your leaking toilet; you’ll keep the cistern water in place and get the flush mechanism working again.

Reason 5: Excess Water Pressure or Faulty Water Valve

Excessive water pressure or a faulty water valve can cause your cistern to leak.

Water pressure that is too high can put unwanted strain on many cistern components like the fill, inlet and float valves. It can also cause leaks or even damage to the flush mechanism. A water valve that doesn’t close properly will allow water to flow into the cistern continuously and cause it to overflow or leak into the toilet bowl.

Common signs of excessive pressure include water spilling into the overflow tube or visible drips coming from the cistern. Addressing the issue can involve adjusting the water flow, replacing worn-out parts or installing a pressure regulator. But you’ll be better served calling a plumber.

Why You Need a Licensed Plumber

When it comes to fixing a leaking toilet cistern, calling a licensed plumber is often the best option. Here’s why:

• Expert knowledge: Licensed plumbers know how to precisely fix issues like faulty inlet valves, flush mechanisms or rubber seals.
• Avoid costly mistakes: A DIY fix like replacing a seating washer might seem easy. Do it incorrectly though and it could result in further damage that may be costly to repair.
• Save time and stress: Professionals will quickly diagnose the problem, whether it’s a worn flapper valve or damaged flush pipe seal and fix it fast.
• Work guaranteed: Most plumbers offer a warranty on their work.

It’s also worth knowing that many plumbing repairs more complex than a simple washer or rubber seal replacement must by law be completed by a licensed plumber. At least you can be confident they will get your toilet working properly while also preventing water waste and future problems.

Fix Your Leaking Cistern Before It Becomes a Bigger Problem

You might initially consider a toilet cistern leaking a minor issue. Ignore it though and it can quickly lead to water waste, higher water bills and water damage.

Whether it’s anything from a worn-out rubber seal to excess water pressure, identifying the cause early will save you time, stress and money. Regular maintenance and timely repairs will keep your flush mechanism and cistern in peak condition. If in doubt always call a licensed plumber to get your toilet fixed right and fast.

Don’t let a leaky toilet disrupt your day or your budget – fix it now and enjoy a smooth flushing experience!

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