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How to Fix a Running Toilet? DIY Tips & Contractor Cost

We put together a guide on how to fix a running toilet. You will find practical DIY tips, materials and products to use as well as the cost of hiring a contractor to do the job.

Every home has at least one toilet. Some homes are linked to the mains drainage while some are linked to septic tanks or other solid waste removal or recycling system. Their purpose is to remove human feces and urine hygienically to a place of disposal. This operation must be carried out safely and securely with separation of the waste from humans being maintained at all times.

There are two main types of toilet namely the seat type (or ‘western’ toilet) and the squat type (more common in the eastern countries). There are also subdivisions of these two types:

  1. Water flush
  2. Dry toilet

All these different types have their own pros and cons but these differences and similarities are not going to be discussed today. Instead we will be talking about the water flushing toilet and what to do if the water doesn’t stop running.

Flush toilets

Toilets which are linked to the public mains drainage system or a private septic tank flush all solids into the drain using a flow of water. These are known as flush toilets. All toilets that are sold for use with the mains water supply must comply with certain requirements and regulations. Different countries have their own water use regulations and with fresh water becoming scarcer, they are becoming stricter and more water efficient every few years. At the time of writing, the US standards in particular, state that all new toilets (known as High Efficiency Toilets or HETs) should ideally:

  • Use no more than 1.3 US gallons (4.9L) water in each flush
  • Remove all fecal matter with one flush
  • Not plug
  • Not produce any odour
  • Be easy to clean

Some flush toilets have a facility to allow two types of flush (or ‘dual flush’) delivering two different quantities of water depending on whether there are mainly solids or liquids to be removed.

You can see therefore that there is a legal requirement placed upon the manufacturer and the user to use the minimum amount of water possible to do the job and not to waste water. If that is the case then what will happen when things start to wear or break and the water flow is continual? We call this a ‘running’ toilet. Today we are going to discuss:

  1. What causes a running toilet?
  2. How do you repair a running toilet?
  3. Who do you need to hire to fix the problem?
  4. Can it be done as a DIY job?
  5. As a last resort should we buy a new toilet?

In order to answer these questions we will need to know a bit about the flush toilet, how it developed from ancient sanitation methods and what parts make up the modern flush toilet.

Flush toilets in ancient times

Flush toilets have been found in the ruins of houses in the Indus Valley in India dating from the third millennium BC. There have also been toilets using hydraulic technology to wash solids away dating from the days of the Roman Empire. However, when the Empire fell, so the toilets fell into disrepair and were eventually forgotten. Fast forward just over a thousand years and a forerunner of the flush toilet was developed in 1596 using a flush valve. One was produced for Queen Elizabeth the First, but the majority of the population used the same unsanitary methods they had been using for a thousand years.

In 1775, Alexander Cumming designed the ‘S’- trap which allowed standing water in the toilet bowl to act as a seal and prevent foul air from escaping the sewer.

It was only with the industrial revolution in the mid nineteenth century and advances in mass production that the flush toilet gained in popularity and became attractive as an aid to health and sanitation.

Sir Thomas Crapper held nine patents in the late nineteenth century for improvements to the water delivery in flush toilets which eventually culminated in the syphon system of water discharge rather than the floating valve system (Contrary to popular myth this person did not invent the flush toilet although he did improve it immensely).

In America the chain-pull indoor toilet was first introduced into wealthy homes and hotels soon after its invention in Britain in the late nineteenth century. In 1907, the vortex flush toilet bowl was designed to self-clean, followed soon after by the flush rim with multiple flush jets delivery system.

In Australia the Caroma Company in 1980 developed the Duoset cistern with two buttons delivering different amounts of water as a water saving device. Modern versions of the Duoset device are now used in toilets worldwide. They save over half of a household’s normal water usage.

What parts make up a flush toilet?

The flush toilet consists of the following components:

Water inlet. Clean water enters the cistern from either a holding tank or direct from the mains water.

The Cistern. This is a small tank designed to hold enough water for one flush. Within the cistern is a float valve which slowly closes as the water level rises. When the water reaches a predetermined level in the cistern the float valve prevents any more water from entering the cistern from the water inlet pipe. As well as the float valve there is also an overflow exit to allow the water to safely exit the cistern if the float valve malfunctions and the inlet water is not turned off. There is also a syphon outlet which is activated by push button, handle or pull chain operated by the user. As the water syphons out of the cistern the water level drops opening the float valve allowing more water to enter the cistern. The syphon discharges the clean flushing water through a pipe to the rim of the bowl.

The bowl. The water from the syphon enters the bowl at the rim and is distributed evenly around the rim to provide cleansing jets discharging into the bowl. On top of the bowl are a seat and a lid.

S-trap. At the lowest point exit of the bowl there is a horizontal S-trap positioned such that there is always a clean water barrier separating the bowl from the drain. All waste is pushed past the S-trap by the force of the discharging water and enters the mains drainage. After the cistern has discharged its capacity, there remains a clean water vapour trap between the bowl and the drain.

What things can go wrong?

In the previous section we talked about the various components comprising the flushing toilet. It should be obvious that there are only a few things that can go wrong with the ‘water in – water out’ method:

The water enters the cistern. This is basically just a pipe entering a water tank. There is a hole near the top of the cistern through which a pipe leads to the float valve. The waterproof seal between the pipe and the cistern can become worn and cease being waterproof causing leaks from this point.

The float valve governs the water level within the cistern. At the end of the water inlet pipe there is a simple lever operated valve. The lever is connected to an extended arm onto which is fixed a float. When the float is at its highest position (meaning the water level is highest) the valve is turned off.

At any other water level the float is lower so the valve is open allowing ingress of water. If the float develops a leak and fills either partially or completely with water so that the float does not sit at the correct level, the water level information controlling the inlet valve will be false. When this happens the float valve will never turn the water off. Sometimes the inlet valve becomes jammed open either by a piece of grit stopping the valve from closing or by washers becoming worn and not giving a watertight seal. If the water level becomes too high there is an overflow vent within the cistern allowing excess water to exit into the bowl or discharge to outside the house. In these cases the float is not operating correctly and the water will not turn off. This can cause a running toilet.

The handle opens the syphon discharge. On high level cisterns (those positioned over six feet from the floor) there is a chain connecting the syphon lever to the user’s hand. On low level cisterns (either directly coupled or with a short connecting pipe) there is either a handle or a push button (let’s assume we have a handle) connecting the user’s hand to the syphon. When the user wants to flush the toilet, the handle is turned, operating a flap valve which pulls a piston thus opening the syphon mechanism.

The weight of the water in the cistern pushes the water (aided by a syphon effect) and discharges through the discharge pipe into the toilet bowl. The handle can become dislocated from the flap valve so that the user cannot open the syphon. The piston within the syphon mechanism has a waterproof washer preventing water from entering places in the syphon that it shouldn’t. These problems can cause the syphon to malfunction thereby either preventing the syphon from opening and discharging the water or by preventing a watertight seal within the syphon. These permanently allow water to flow from the cistern through the syphon into the bowl. This can cause a running toilet.

The water circulates around the rim. When the water exits the syphon, it is channelled into the hollow rim of the bowl where it discharges under pressure into the bowl, washing any solids into the first half of the S-trap. If you live in a hard water area or you have old iron water pipes, minerals can be deposited inside the rim and partially block the openings. This slows down the discharge from the cistern and prevents the moving water from doing its cleaning work properly. You can buy a water softener to remove the mineral deposits or have a cleaning routine which removes the solids. We will talk more about this in the Maintenance section later on.

The incoming water exits through the S-trap. The incoming water collects in the bottom of the bowl and makes the water level in the bowl rise. There is now an imbalance of pressure on either side of the S-trap. The imbalance causes the water to flow from the bowl, through the S-trap and into the drain. This effectively carries away any waste solids or liquids. When the water ceases discharging from the cistern the water level in the S-trap lowers until it is at its normal level. The standing water in the S-trap separates the clean air in the room from the foul air in the drain. If the drainpipe is blocked downstream from the toilet because of a build-up of solids, then the increased air pressure on the downstream side of the S-trap will prevent the water in the toilet bowl from discharging properly. To remedy this you will have to unblock the pipe either at the S-trap or further downstream wherever the blockage is sited. If you cannot do this yourself then a plumber needs to be called.

A running toilet

From the previous description of possible flush toilet problems we can see that the only way you can develop a running toilet (that is a toilet that will not stop trying to fill) is if there are problems with the water inlet float valve, the float or the syphon.

What are the signs of a running toilet?

You have just flushed the toilet and rather than the water turning off after a few minutes when the cistern is full, you continue to hear water trying to fill the cistern. If you cannot see any water running into the bowl then you have an external overflow pipe (some overflow pipes discharge into the toilet bowl and some discharge from an external pipe through the wall) and the water in the cistern is running away down the overflow pipe.

Is the flush handle stuck?

If your toilet has a lever for the user to flush then sometimes the handle can become stuck in the down position meaning that the syphon is open and the water is running out of the cistern as fast as it is entering. This can also happen if you flush with a button, and will not stop until you have unstuck the button. To fix a faulty lever may need its locknut adjusted. There is a threaded spindle going through the cistern wall which connects the handle to the syphon. There is a locknut threaded onto the spindle which keeps the handle in place. Sometimes the handle can become jammed. This is simply fixed.

  • Turn off the water either at the mains stopcock or at the toilet isolation valve
  • Unscrew the locknut as far as it will go and wipe the thread and the part which goes through the cistern wall with a damp cloth to remove any particles of rust, grit or whatever
  • Check the washers between the locknut and the cistern and between the cistern and handle. They may be worn or perished and might require replacing
  • Apply a smear of silicone grease (if you haven’t got any silicone grease then Vaseline will do) onto the thread and onto the part which goes all the way to the handle
  • Re-tighten the locknut. Tighten it as far as it will go all the while ensuring the handle will turn easily

Have a look inside the cistern

The cistern (that is the water tank) has a lid to stop the water from evaporating and to stop anything from falling into the water. With most types of cistern, the lid just sits on top of the cistern body with no fixing method apart from its self-weight. The types of cistern with the flushing push button on top require the button to be removed before you can lift off the lid. Each model is different so try to figure it out for yourself or look online for specific instructions relevant to your brand of cistern.

Lift off the lid and look inside your cistern. See if you can work out if the water is discharging through the syphon or out of the overflow pipe. Try to figure out how the mechanical bits inside work. Don’t worry, there isn’t any high tech gadgetry inside, someone from the nineteenth century wouldn’t really notice much difference compared to their cistern. A good eye and a bit of intuition will probably allow you to work out how the flush works.

Look at the overflow pipe

Toilet cisterns have an overflow pipe to stop the water from filling the tank too much and spilling out all over the floor. Some overflow pipes exit the cistern through and near the top of the side wall, in which case the pipe will carry on through the wall of the house and discharge outside. There will probably be a mesh filter over the open end to stop insects from gaining access to the house through the pipe. Check the mesh to see that it is not blocked.

Even if the water isn’t at the level of the overflow pipe, some day it might be and then you will wish you had kept it clean. Some cisterns have a vertical overflow pipe which discharges into the toilet bowl. Either way, you have an overflow pipe that gets rid of excess water. If the water level is above the inlet of the overflow pipe then the problem may be with your float valve (sometimes called a ballcock). By the way, if the water level is much below the overflow level then the ballcock may be adjusted incorrectly anyway so it is worth having a look at that.

Have a look at the float valve

As said previously the float valve (or ballcock) is a float fixed to an arm which opens and closes the water inlet valve depending on the water level inside the cistern. When the cistern is empty, the float is at its lowest position and the valve is open allowing water in, when the cistern is full the float is at its highest position and the water inlet valve is closed. If the water won’t stop running into the cistern check to see if the float is being prevented from moving as it should and check to see if something is stopping the valve itself from closing. Perhaps a piece of grit.

Try holding the float and lifting it up as far as it will go. If the valve closes and the water flow stops then the float position will need adjusting manually. Sometimes there are screws and sometimes a clip holding the float in place. Sometimes the float is permanently fixed onto the arm and you have to bend the copper arm slightly to change the float’s position. Loosen the fixings so the float can move along the arm. Adjust the float along the arm until its position allows the valve to close completely. Tighten the fixings to hold the float in position.

Check the syphon

When you turn the flush handle or pull the flush chain on the cistern, the handle moves a lever which lifts a piston within the syphon. Water is then forced through the syphon producing the syphoning effect which empties the cistern into the toilet. If you don’t know how a syphon works then look online, they are quite fascinating. There are plenty of websites just dying to teach you all about the syphon principle.

Sometimes the watertight seal that stops water from entering the syphon around the piston rod fails and water fills the wrong side of the piston. When this happens the syphon will not work properly and water continually discharges into the toilet bowl. The easiest way to fix this is to buy a new syphon component and replace the old one. They don’t cost much and are very easy to fit.

Turn off the water

Remember that before you start to replace components or remove pieces from inside the cistern you will have to turn the water off.

Tools needed to fix your flush toilet

The tools you need will depend on the item that needs to be repaired, but in general if you have the following tools then you probably won’t need anything else.

  • Hacksaw
  • Pliers
  • 2 x adjustable wrenches
  • Screwdrivers to suit the size and type of screws
  • Pipe wrench

Materials you might need to fix your flush toilet

The materials you might need will depend on the job that needs fixing. The following items are useful to have available.

  • Plumber’s PTFE thread tape
  • Silicone grease (or Vaseline)
  • Spare water inlet valve, float and float rod. (The float, float rod and inlet valve might be available ready assembled as one piece or might be sold individually)
  • Spare syphon
  • Spare flushing lever handle and washers

DIY or contractor

As long as you follow a simple rule, fixing a running toilet is well within the skills of the most basic DIY enthusiast.

The simple rule is “Isolate the water from the cistern before starting”.

As long as you stop the water from entering the cistern by turning the water off at the mains or by turning off the inlet isolation valve, then anything you do wrong will not cause any great problems. The worst you will need to do is buy a new cistern.

However, if this is your only toilet in the house then you have another more urgent problem but that is another story.

But we are not going to damage anything, are we? Just take it easy and go through each step, one at a time. Just read and obey the following points and all will be well.

  • Turn the water off before you start to disassemble the toilet.
  • Work through each item on your checklist and see which one is causing the problem.
  • Replace or repair each broken component as you find them (there may be more than one!)
  • Don’t forget to tighten all threaded joints to hand tight and then tighten a little bit more with a wrench.
  • Don’t forget to tape all threads with PTFE thread tape to ensure a watertight seal.
  • Don’t forget to replace all rigid and flexible washers back where they came from.
  • Turn the water on at each stage to see if the problem has been fixed.

If however you cannot cope with DIY, either because you haven’t got the skills or the confidence, or even if you haven’t got the time then the next option is to call in a contractor.

The most obvious contractor to choose is a plumber. But don’t just choose anyone who calls themselves a plumber. A reputable plumber will need to have the following requirements.

Plumbers have to be licensed. Most states insist on plumbers being licensed. Check that their license is current and that they do not have any active complaints against them. A licensed plumber will be able to provide you with a phone number to call to check on the validity of their license.
Workers’ compensation insurance. This is insurance cover in case the plumber or any members of the plumbing team are injured while working on your property.

Liability insurance. This is insurance cover in case the plumber causes damage to your property or causes injury and death to you or anyone else. Cover should be for a minimum of $500,000.

Certification. You need to know that the plumber is qualified to do the work you are asking. Plumbing is a very wide occupation, ranging from lead work on roofs to installation of gas central heating. You need to know that the person you hire has the skillset to do your work. As we have said before, repairing a toilet is a very easy job and if most DIY people can do it then a qualified plumber can too. But there is no harm in checking his qualifications and seeing what his competencies are.

Professional Association. If your plumber is a member of a professional association then you can be assured that they are fully qualified and have received the latest ongoing training.

Be aware that plumbers are an expensive trade to hire, because of the many facets there are to the skillset. Most plumbers will charge a call-out fee which usually turns out to be a minimum charge of one hour no matter how small the job is. You must also be aware that if you call out a plumber outside normal working hours or at weekends and public holidays, you can be sure to be charged a premium rate. If there is a problem with your toilet flush and it happens at night, it would probably be far cheaper for you to turn off the water to the cistern and leave it until the following day before you have the plumber out. Bear in mind that you don’t need the cistern working to flush the toilet. Just pouring a bucket of water into the toilet bowl will flush away any solids or liquids.

Most plumbing work is not necessarily difficult it just needs a lot of specialist knowledge. You need to know building codes and regulations; spare parts knowledge as well as knowing what materials you must use for a specific job. This all comes with experience and training and that is why a plumber is so indispensable.

The cost to do the job

The cost to repair a toilet will depend on what is wrong with it. The following tables list typical prices for hiring a plumber to do the job and also typical prices to buy spare parts and tools if you decide to do the job yourself. Note the prices are a guide only and amounts will vary depending on quality of product. Prices of parts and tools will also vary depending on where you purchase them. As a general rule, specialist plumbing suppliers will be more expensive (but sell better quality products) than cheaper bargain stores and online.

Cost to repair a toilet
Low end$80
High end$500
Typical range$130 to $300
National average$210
Cost to hire a plumber
Low end$90
High end$800
Typical range$170 to $450
National average$310
Hourly rate$45 to $150 per hour
Cost to install or replace a toilet
Low end$120
High end$810
Typical range$220 to $530
National average$370
Toilet plunger$20 to ?30
Hacksaw$4 to $20
Pliers$5 to $25
Pipe wrench$20 to $60
Adjustable wrench$12 to ?35
Spare parts
Toilet with close coupled cistern$150 to $400
Toilet seat$30 to $50
Syphon valve unit$40 to $99
Push button flush syphon valve$75
Diaphragm syphon washer$25
Float valve$9 to $35
Float valve repair kit$6 to $35
Flexible toilet connector$5 to $25
Faucet & valve grease$5 per 1fl oz. tube
Silicone grease$3 to $8 depending on size
PTFE thread tape$5


If you decide to repair or replace your flushing toilet yourself you will have a far better experience if you follow some simple common sense rules.

Lifting. Toilet bowls and cisterns can be heavy. Get someone to help with lifting if you need to remove your old one or if you are manoeuvring the new one into position.

Electricity. Be careful if you are using electrically powered tools or lighting when near water.

Hygiene. You will be working on and handling parts of a toilet. Do not eat, drink or smoke while working. Wash your hands after work and before handling food. If possible wear protective gloves to keep your hands clean.

Cutting tools. Saws and utility knives can be sharp. Take care when using them and always have a first aid kit nearby.

Dust. If you are involved in cutting or drilling operations, always wear safety spectacles and a dust mask.

Follow the instructions. Always read the manufacturer’s fitting instructions carefully before attempting any replacement or repair.

Maintenance tips

As with all things, preventing a problem is better than fixing a problem. Your flushing toilet is no exception. Luckily such an efficient piece of equipment has surprisingly few moving parts.

We will now look at a few tips to help you maintain the toilet and cistern and help prevent any problems from occurring.

A common problem with toilet cisterns is when the float valve (ball cock) becomes stuck because of worn parts and corrosion. Regularly check the movement of the float to see that it moves up and down easily and without any resistance. If there are problems with moving the arm then check to see if the washers need replacing.

Check that the water level is at the correct height. You may be able to see water staining on the inside of the cistern walls which will tell you if the level has dropped recently. If necessary you can always bend the float arm slightly or move the position of the float along the arm to remedy the water level.

If the float is part of a plastic assembly, then there will be a nylon nut on the ball valve which adjusts the angle of the float arm. This must be adjusted to change the height of the float. When turning the nut, do not use too much force as nylon nuts are notorious for breaking.

If the water flow into the cistern is a bit sluggish, check that the filter in the inlet valve isn’t clogged and preventing the water from passing through.

If you need to empty the cistern of water in order to do a repair or replacement, just flush the cistern and the water will empty into the toilet. If it won’t flush then use a cup to remove most of the water. You can then use a bath sponge to mop up any remaining water from inside the cistern.

If it is the cistern itself that is leaking then the leak can be fixed using sealant from the inside. Mop up as much water as you can and allow the surface to dry out before applying the sealant. This will do as a temporary job until the cistern can be replaced.

If there are bigger holes or cracks in the cistern then they can be repaired using epoxy resin or plumbers putty. Once again remove all the water and allow drying out before attempting the repair.

If your cistern is noisy when filling up, you can fit a silencer tube. This is a tube that diverts the water from the inlet valve directly to the bottom of the cistern. Be aware that the tube must be manufactured from soft rubber or flexible polythene otherwise if there is any negative mains water pressure the water in the cistern may be sucked back into the mains. This is illegal in most countries so ensure the silencer tube is flexible so it will collapse on itself if siphoning occurs.

Other loud noises can be caused if the mains water pressure is very high. High pressure water can make the ball valve bounce or jerk, sending vibrations back along the pipework.

If you live in a hard water area or have old iron water pipes supplying your house, you will have problems with iron staining and deposits in your toilet cistern. The red colour will stain the inside of your cistern where water often stands for hours at a time. Do not use bleach on rust stains as it will set the stains. Regularly check the inside of your cistern for a build-up of sand, grit, corrosion and other debris, Over time this can produce a foul smelling toilet as well as cause blockages in the mechanisms. You can buy chemical cleaners specifically for cisterns from supermarkets or if you wish, a simple cleansing solution to remove stains as well as normal dirt can be made as follows:

  • Make a cleansing solution with 1 part white vinegar to 4 parts water. Pour into a spray bottle and shake to mix thoroughly.
  • Turn off the water to the cistern by closing the main stop valve or closing the isolation valve.
  • Remove the lid of the cistern and place safely to one side. This will also mean you must move all those spare toilet paper rolls and other things from on top of the lid.
  • Flush the toilet to remove most of the water from inside the cistern. Use a sponge to remove any remaining water left in the bottom. It is likely you will see some sand or other solids in the bottom.
  • Spray the inside of the cistern thoroughly with the contents of the spray bottle. Use a clean rag or paper towels to clean the walls of the cistern and wash any solids down to the bottom.
  • Use more paper towels to mop up the remaining water and the solids until all debris has been removed.
  • If needed you can always use a scrubbing brush to remove stubborn deposits.
  • Turn the water back on and allow the cistern to refill.
  • Flush the cistern a couple of times to remove the last remaining traces of unwanted dirt.

If you have problems with rust stains from hard water you can install a water filter designed to clean the mains water when it enters the house.
When you clean any part of the toilet always use rubber gloves.

Close the lid of the toilet bowl to prevent germs spreading from water splashes when flushing.

If you have problems with maintaining a strong flushing pressure from the cistern there are a few things you can try to increase the power of the flush.

  • Partially open inlet valve. If the inlet water valve is not fully open, the water will not enter the cistern at its correct flow rate. Turn the valve counterclockwise with your fingers until the valve is fully open.
  • Check water level. Lift the lid from the cistern and check the water level is about 1” below the overflow outlet pipe. We have talked before about how to adjust the float valve to change the water level.
  • Clogged rim. The flushing water enters the bowl through small holes located on the underside of the rim. If you have hard water these holes can become clogged by lime scale and other deposits. Inspect the holes around the rim using a small mirror and clean them by brushing vigorously with a nylon brush. This will increase the toilet’s flushing performance.

Video Resources

To finish

Today’s article was all about what happens when your flush toilet continues to waste water after a flush. In order to understand how this happens and what to do about it, we first of all needed to understand the operation of the various components that make up a modern flush toilet. We talked about the legal requirements of a toilet and realised that one of the most important is that it must not use too much water when flushing. After talking about the components of the toilet, we then discussed the things that might go wrong with the simple mechanisms controlling the flush. We talked about what to look for when you suspect there is a problem and how to correct the problem.

We talked about fixing the toilet as a DIY project and the basic tools and spare parts we would need to do the job. We also talked about hiring a plumber to do the job for us. Then we talked about the various costs involved in repairing or replacing a toilet followed by some safety considerations to think about if we want to stay healthy. Lastly we talked about the importance of preventative maintenance with your toilet and how we can stop things from going wrong by just checking the moving parts now and again and replacing parts before they become a major problem.

I hope the information we have discussed today has been useful for you as a way to keep your home well maintained and in good working order.

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