Here are several ways you can investigate and stop a leaking toilet.
First, Let’s Determine Where and What the Leak is
When it comes to a leaking toilet, there are two different sources – feed water and waste water.
Even though the water is ultimately from the same source, the toilet, finding which part of the toilet is leaking is where you need to start.
It doesn’t matter what kind of toilet you have or how old it is, they can be viewed as two separate parts, even when your toilet looks like it’s one piece:
Toilet Cistern
This is the cleanest part of the toilet in terms of waste. A small – usually 8-12mm copper or plastic pipe – feeds your toilet the clean water it needs to flush effectively. The cistern itself holds enough water so it is ready to go when you need it.
Quick Note: if this sounds a bit basic to you, feel free to go to the outlined sections below and skim the rest. This is aimed at everybody at all levels of DIY skill and keeping it plain and simple allows more people suffering home emergencies involving leaks to resolve it themselves or be armed with knowledge when calling a professional.
When your toilet is flushed, it releases anywhere up to six litres of fresh, clean water depending on the plumbing installed. A diaphragm usually lets the water escape into the toilet pan when the handle is pulled or button is pressed. Once the cistern is empty, an inlet float valve lets new water in until it fills to a preset level. Once full, the water sits there until needed again.
The most common places for a leak to occur when it comes to toilet cisterns are:
The feed pipe entering the cistern, usually caused by worn seals.
The seals where the cistern meets the toilet, either via a “flush tube” or direct connection.
The cistern overflow is running constantly. If this runs to an external overflow pipe, the seals connecting the cistern to the overflow pipe may be at fault.
Sometimes the cistern itself can be at fault but if this is the case, the leaking is likely to be more like a flood due to the volume. The inlet valve would keep filling as it’s supposed to, as the water level would not reach the level where it’s supposed to shut off.
The easiest method of checking faulty seals is visually. Establish where the leak is coming from, for example, the nearest joint to the cistern from the incoming pipe. Isolate the incoming water from the nearest isolation valve. If there is no nearby isolation valve, you may need to turn off the water to the whole property.
How to Fix a Leaking Pipe or Toilet Cistern
Must-Have for Plumbers and DIY’ers
PTFE Sealant Tape
Plumbers sealant tape made from Teflon, this stuff is great in a pinch! Use on feed pipe connections and joints.
For Close Coupling Toilets
Close Coupling Toilet Seal Kit
A handy kit for replacing the seals where the cistern meets the toilet. Includes new doughnut washer and cistern bolts and washers.
For Fixing Leaks around the House
O Ring Seal Washer Kit
A selection of popular O rings and seals for plumbing and other uses. A handy box to keep for home plumbing emergencies!
Next you will need to disconnect the pipe connection you think is leaking.
Water feed pipes are generally just past hand-tight and as it will have been a long time since being tightened, you will likely need an adjustable spanner to loosen enough to undo the pipe by hand.
If there are two nuts on the same connection, such as an elbow (90 degree bend) or straight connector, you may find it easier to unscrew by using two pairs of adjustable spanners, using one to hold the opposing nut in place as you loosen the other.
Once disconnected, you can inspect the seals within the joint. They usually sit within the nut to stop water escaping when installed. The seal is the weakest part and most susceptible to wear and tear.
The most common seals to fail are rubber or plastic seals and washers where metal meets plastic, such as where the copper water pipe ends at the cistern and meets the cistern inlet valve connector, on the outside of the cistern.
WARNING – Please be careful when loosening and tightening metal nuts on plastic threads, the metal part can easily ruin the thread on the plastic part and make it impossible to seal again when tightened.
Just make sure to not cross thread it and not over-tighten!
If you can see the seal is not uniform in shape, or damaged in anyway or clearly not a flat disc anymore, then simply remove with a finger or small tool – even a small knife will do the trick – and replace with a new like-for-like seal.
If you can’t be certain of the size and don’t want to risk ordering the wrong size online, you can take the original seal to a local plumber’s merchant or DIY shop to compare or ask staff for an exact new replacement. Usually, however, a box set like the one shown above will cover all sizes and if you know the size of your pipe, this makes it easier.
15mm Nylon Flat Washer Pack
This is the most likely replacement seal you will need if the culprit is where copper meets plastic near the toilet cistern. Simply remove the old one with your fingers or small tool, and place one of these in its place. Make sure the area is clean and the entire old seal is removed. Any obstructions or grit can prevent a good seal.
Place the new one flat and fully into the bottom of the inside of the nut, then carefully push the pipe back together and tighten. Make sure the nut isn’t cross threaded, easily done by ensuring the two parts line up nicely and checking the nut is aligned flat with the opposing part, rather than lopsided.
Test by slowly turning the water back on make sure to keep a light and dry paper towel handy.
What to Watch for:
- The repair should outwardly look the same as before you started
- The old seal should be fully removed, including any broken bits
- The new seal should be placed in the same place and orientation as the old
- Make sure any internal parts you can see are clean and free from dirt and grit
- Tighten by hand and finish with a spanner
What Not to Do
- If you are unsure about any part of this kind of repair, find someone confident with DIY-type repairs or a plumber.
- Don’t feel bad if you need help by doing the above
- DO NOT over-tighten, especially metal nuts on plastic thread. It will easily strip the part and make unsable
- Do not turn the water back on fully until you are satisfied with the repair, and do not turn the water back on too quickly
If the cistern is leaking but not from the problem above, check out our How To Replace a Flush Mechanism article as it specifically deals with the ins and outs of taking apart a cistern and any seals that need replacing for specific parts are covered here.
If You Find the Toilet is Leaking…
If you find water is escaping from the toilet itself, chances are it’s the pan connector.
Unless you can see visible damage to the toilet such as a crack or hole on the toilet itself, it’s going to be the cistern above or pan connector below.
What is a Pan Connector?
A pan connector connects the toilet pan to the waste pipe from your toilet. There are many variations and types but this is all it does. One end is bigger and seals around the back of the toilet and the other end is smaller and fits to a 4″ (100mm) waste pipe that then takes the flush away, never to be seen again.
Here are some of the more common types of pan connector used in the UK:
Universal Straight Pan Connector
McAlpine Straight Fit Connector
4″ (110mm) connector suits all toilet pans. Patented “lock-ring” inlet for best the seal possible.
90 Degree Bend Pan Connector
Adjustable length on waste pipe connection end, 170 > 250mm to allow a good fit.
Offset Pan Connector for Awkward Spaces
40mm Offset Pan Connector
16.5 x 14 x 13 cm length, with 40mm difference between pan and waste pipe connections.
Much like the feed water and cistern end of a toilet, there are only so many things that tend to leak from a toilet.
Assuming the toilet itself is free from damage and you’ve already checked the cistern out, it’s more than likely to be either end of the pan connector. The toilet is a solid mass of porcelain, so the weak points are once again, seals.
But how do you know the pan connector is leaking?
- The leak is visibly worse when the toilet is flushed.
- The water is not clean, though this is not a certainty as chances are you are testing by flushing with fresh water.
- The water is only present around the back and bottom of the toilet, not dripping down from above.
- The pan connector is not lined up properly and water escapes when flushed, or water level in toilet pan is lower than it should be.
A standard pan connector has two seals, one at each end. Like the above, these are the most subject to wear and tear.
A leaking pan connector can be much worse to find and deal with than a fresh water leak, but equally can be easier to replace (depending on access and working space).
Let’s assume you have room to work and enough access to work with, how do you change a pan connector?
The handy thing with pan connectors is, it’s fairly obvious which end goes where and you have two solid ends to connect to, the toilet itself, which is should be unmovable, and the waste pipe, which should be firmly in the floor or wall, depending on where it runs to.
Here’s how to replace a pan connector:
Step 1
Give the pan connector a wriggle, just to see how much give you have. Pull the pan connector away from the toilet, as this is normally the easiest side to remove from. Now pull the rest of the pan connector out from the waste pipe.
Step 2
Check you have the larger end of the pan connector facing the toilet, and pull the pan connector onto it. The toilet end of the pan connector fits on over the toilet outlet. Now push the smaller end into the waste pipe, as the seal on this end is internal whereas the toilet end is external.
Step 3
Clean up the area and make sure the floor and around the toilet is completely dry. Place some paper towel where the leak was for testing in the next step.
Step 4
For ease of testing, you may want to colour the water you’re testing with. This can be with food colouring or drain dye, or any other way you can think of. This allows you to see exactly where any new leaks are. If there are no coloured or new water drops, then that’s it!
Step 5
If there is still a leak, or a new one, just check the parts are lined up and as a last resort, remove the new pan connector and check the seals are still intact. If anything has shifted, put it right and try again. Sometimes just wriggling the connector until it’s snug is enough to make it seal.
Drain Dye – a Much Easier Method of Testing for Leaks
Simply Add to Water in the Cistern and it Will Show You Where the Leak is!
Used by countless plumbers and drainage professionals for speed, convenience and piece of mind
- Non toxic
- Use in small amounts, this stuff lasts for ages
- As a dry powder, it can last for a long time, in case you get leaks in the future
- The colour shows very easily in deep, dark places
Hopefully this will have helped you resolve your leaking toilet, but what could have caused it?
What Causes a Toilet to Leak?
Common Causes
Let’s split this into two again, clean and waste:
Fresh Water Leak from Toilet
- Wear & Tear
You use the toilet, it flushes, you forget about it. Someone else uses it, same again. There’s always water there waiting for you to release it and then it flushes, the cistern empties and then is filled up with nice, clean water. All day, everyday.
But every time you use your toilet, the water that was waiting in the cistern is gone, flowing away into the drainage system via the toilet. Once emptied, the inlet valve in the cistern opens and the water pressure from the feed pipe pushes new water into the cistern. Once it reaches the set level, the inlet valve closes.
During this process, there could be anywhere up to 4 seals between the feed pipe and inlet valve that exist only to stop water escaping through the joints.
So imagine all day, everyday, for years, these seals are having to deal with water under pressure and not only stop it escaping, but the inlet valve especially has to keep the water trying to get into the cistern at bay, until needed again.
The seals can wear down over time. Going hand in hand with wear & tear:
- Hard Water and Scale Build Up
Areas with hard water cause a lot of hassle for the water authorities and consumers alike.
From making tea and coffee taste funny because of the kettle scaling up to making cleaning the toilet more difficult, hard water can also cause deposits to build up in the pipe work system.
In fact, both feed and waste pipes can be heavily affected by hard water and scale build up.
When it comes to the process above, those seals are not only controlling the flow of water, but when scale builds up inside the pipe, this can affect seals by building up around the seals themselves. This can increase wear by eating away at the plastic or rubber seals and make it difficult to keep a seal when the pipe is no longer clean inside and the seal cannot do it’s thing as it needs a clean, flat surface to seal against.
Another process that can potentially speed up wear & tear are:
- Cleaning Products and Additives
Cleaning chemicals, as much as they are designed to be gentle as much as they are effective, can also increase the wear on seals. Though in this case, since cleaning chemicals can only be placed inside the cistern or toilet, they only affect the internal part of the cistern and then the toilet itself.
Which brings us to…
Waste Water Leak from the Toilet
All of the above can be applied to the toilet itself. except that the only seal is the connection from cistern to toilet and then pan connector taking toilet outlet to waste pipe. There are no active parts to the seals as there is no pressurised water feed pipe at this point. it’s all gravity.
But the hard water and cleaning chemicals, additives, etc. can all wear down the pan connector.
Other Causes of Toilet Leaks
- Pipe being knocked or hit by other objects
- Other nearby repairs, such as changing nearby or related feed pipes, as sometimes this can jolt or dislodge other parts on the verge of leaking. Especially in older properties.
- Poor or convoluted installation. Pretty self explanatory, but sometimes pipe can be made to work when it shouldn’t! Eventually it give up but unfortunately this can be when the plumbers are long-gone…
Conclusion
There are a multitude of reasons why a toilet can leak, and it’s usually at the most inconvenient times, such as when you have guests over or during the holidays. This could be coincidence but also could be the extra usage speeding things up.
This article has hopefully helped you out, but if not, there are other more in-depth articles and posts on www.drainhub.uk and we will link any related content below.
In the meantime, let us know if we’ve missed anything or not made it clear enough by getting in touch!
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