How to fix a running toilet: Here we explain how to diagnose and fix the cause of a running toilet. If you hear your toilet tank refilling when the toilet is not in use, or if there is always condensation on the toilet tank, you are wasting water and you may be ruining the septic drainfield. More subtle running toilet problems include periodic poor flush of the toilet too.

This article series discusses the cause, diagnosis, and repair of toilet problems (water closet problems) such as a toilet that does not flush well, clogged toilets, slow-filling toilets, running toilets, loose wobbly toilets, and odors at leaky toilets. Here we explain how to diagnose and repair problems with toilets, leaks, flushes, odors, noises, running and wasted water.

Toilet Runs Continuously - Diagnosis & Repair

Is your toilet running? Better go catch it!

That was a joke when we were kids. But a running toilet wastes water and it can flood a septic drainfield leading to very costly septic repairs.

Our page top photo as well as the photograph below both show ugly staining in a toilet bowl - strong evidence that both of these toilets have been running, wasting water, and sometimes giving bad flush performance as well.

[Click to enlarge any image]

And if your building is connected to a private septic system, a running toilet can easily flood and damage the septic drainfield or soakaway bed, inviting a sewage backup into the building.

There are also more subtle but troublesome snafus that occur when a building toilet keeps running. For example in a freezing climate building sewer lines close to the building may not be below the frost line. Instead the sewer line depends on the fact that it slopes to the sewer or septic tank to remain empty and thus immune to freeze-up problems.

But a dripping faucet or a running toilet, by sending a slow trickle of wastewater into the drain system, can cause a drain to freeze and back-up during cold weather.

Readers should also

see ALTERNATIVE & WATERLESS TOILETS for a discussion of camping toilets, chemical toilets, emergency-use toilets, waterless toilets, graywater systems, composting toilets, home health care toilets, incinerating toilets, outhouses, and latrines.

How to Detect & Diagnose the Cause of a Running Toilet

A plumbing leak that causes a toilet to run, the only clues might be noticing that the toilet fill valve is sometimes re-filling the tank even though no one has used the toilet, or one might hear water running in the building drains, or if the property is served by a private septic system, the system may experience flooding and backups.

See PLUMBING DRAIN NOISE DIAGNOSIS for tracing noises to individual toilets or plumbing drains.

[Click to enlarge any image]

• Listen for periodic sounds of the toilet tank filling up even though no one flushed the toilet. Most often you'll hear this sound at night when the building is quiet.
• Look into the toilet bowl for a slight rippling of water on the toilet surface after the tank has filled.
• Look into the toilet bowl for stains (photos at left and at the top of this page) indicating a history of water running from the tank into the bowl.

• Look at the toilet tank for external condensation: in warm humid climates, it's normal for condensation to appear on the toilet tank when it is re-filled immediately after being flushed.
  Our photo (left) shows condensation on a toilet flush tank that was occurring normally after use - this condensation was not present when the toilet had been unused for several hours or overnight.
  
  But if you see condensation on the toilet tank continuously during warm hot weather, or for example, if you see condensation on the toilet tank when the toilet has not been used overnight, chances are the toilet tank is running and the incoming water is keeping the tank cool.
• Try a dye test to check for leaky toilet tanks, fill valves, flapper valves: we use a dash of septic dye powder but we've demonstrated this method using simple food coloring - just put enough red or green food coloring into the toilet tank to color its water, and watch for that color showing up in the toilet bowl below when the toilet has been resting for an hour or more.

Replace Defective Toilet Fill Valve

Above: the black assembly is the fill valve that includes a float and an internal valve that allows water to fill the toilet tank following a flush.

• Bad toilet tank fill valve or valve adjustment: look into the toilet tank - a toilet fill valve that runs continuously and does not shut off will send water over the top of the toilet and down into the toilet bowl.
  
  If you see water running into the top of the overflow tube (and luckily not out of the top of the toilet tank and onto the floor), see if lifting the fill valve's float will stop the water from entering the tank.
  
  If so, an adjustment to the float or float arm that moves it lower into the tank will stop the tank from filling. On the toilet tank vertical float fill valve shown in our photo, our finger is below the control lever moved by the float to open or close this toilet tank fill valve.
  
  Adjusting the screw (also at our finger) moves the float up and down to determine the water fill level cut-off point.
  
  If the toilet tank fill valve is visibly leaking or if you cannot adjust it to work properly, you may need to replace the toilet tank fill valve.

Leaky Toilet Flush Valve Repair

Above: some of the basic parts in a toilet flush valve or "flapper valve". The original flush valve or flapper valve in our first photo is blue.

Second photo above: a red rubber flapper valve from Korky. You can see that the valve's two "ears" simply push over plastic mounting pins on the valve base, and the flush chain hooks between the flush lever and the connection point on the front of the flapper valve.

• Bad toilet tank flapper valve:
  
  the most common cause of a running toilet is a poor seal between the toilet tank flapper valve (at the bottom of the toilet tank in the center).
  
  Our photo above shows the blue toilet flapper valve or flush valve in the open position at the end of a toilet flush - we were holding the flush lever down, that's why the pull chain is taut.
  
  This large rubber or plastic toilet flush valve opens when the tank flush lever pulls it up, floats during the flush operation, then closes to seal the toilet tank during tank refill.
  
  Try pushing gently down on the flapper valve and wiggling it side to side - sometimes this will clean a little debris off of the valve itself or off of the valve seat, and the leak will stop. For a while. Maybe. Well sometimes.
  
  Try cleaning the flapper valve
  
  (shown below): un-hook the flapper valve ears from its hinge connection and, keeping the pull chain attached, simply inspect it for warping, cracks, mineral scale or debris.
  
  If the flapper valve is not damaged or deformed (out of round) then try cleaning the valve itself and the valve seat using a scrubby sponge and scouring powder.
  
  If cleaning doesn't solve the problem of leaks at the flapper valve it's time to replace it.
  
  It's easy and inexpensive to replace just the flapper valve using a kit,
  
  and kits are also available to glue a new valve seat onto the flush valve opening.
  
  Complete flapper valve and flapper valve seat replacement 
  
  is not technically difficult either, but one has to remove the whole toilet tank from the bowl, take apart the old valve and standpipe, and install a new one - more trouble. Before taking these steps, try just cleaning off the flapper valve seat with a green scrubby sponge and replacing the flapper valve itself, leaving the old seat in place.
  
  Watch out:  if you disassemble the entire toilet tank and remove it from the bowl or toilet base, be careful not to over-tighten the toilet tank bolts (see sketch below) that secure the toilet reservoir tank to the toilet bowl. Doing so risks an immediate or future cracked and broken toilet tank - leaking into the building.

Below: this leaky blue flush valve was both deformed - out of round - and covered in algae and a bit of scale. It's best to simply replace a valve in this condition.

If the flush valve is deformed it may not seat properly and it is likely to leak.

The yellow arrows point to discolorations on the under-side of this valve that may mark leak points where the valve was not seating properly.

Remember to clean off the flush valve seat before installing the new valve.

Leaky Closet Spud Gasket Repair

• Leaky closet spud gasket: the rubber gasket sealing the toilet tank to the bowl may be leaky, or fittings securing the tank to the bowl could be leaking.
  Watch out: If leaks are at the toilet tank mounting bolts you will might see water on the floor. But then again you might not.
  
  [Click to enlarge any image]
  
  But if there is a leak at the flush valve mounting assembly or below it, at the spud gasket that seals and cushions the toilet tank at its connection to the toilet bowl, water may leak from the tank directly into the bowl around the flush valve - so the problem (on rare occasions) may be the closet spud gasket, not the flush valve itself.
  
  I know, I replaced three toilet flush valve flappers on a toilet whose bowl showed constant rippling of running water before I figured out that the problem was not the flapper valve but the spud gasket.
  
  How did I diagnose a leaky spud gasket?
  1. Push on the flush valve flapper
     
      inside the toilet tank. If the flapper is leaking often a bit of cleaning of the flapper under-side and of its mating surface plus pushing gently down on it will stop a leak there.
  2. Push down gently on the top of the toilet tank itself.
     
     If the spud valve is leaky because the tank bolts are a bit loose this may slow the rippling into the toilet bowl.
  3. Gently tighten the toilet tank bolts
     
      securing the tank to the bowl.
     
     Watch out: Do not over-tighten the tank to bowl bolts or you may later find that you cracked the toilet tank or cistern - a mistake that can flood a building.
     
     Watch out: While ouir drawing below showing the toilet tank bolts depicts only nuts and washers at the toilet bowl underside, some toilet tank assemblies use two pairs of nuts and washers:
     
     The first pair secures the bolt to the tank or cistern itself, while the second pair secure the assembly to the toilet base.
     
     Unfortunately, toilet spud gaskets are not standard, though there are some general replacements that fit a lot of toilets.
     
     So if you take the toilet apart, do not throw away the old spud gasket before you have found a proper replacement. You might need to clean-up and re-use the old one.
• Check out the septic system:
  
  for signs of backup, blockage, or odors outside. Effluent breaking out to the surface, muddy or soggy areas, smelly areas, may indicate that the septic system, or part of it, are failing and are periodically not accepting waste.
• Call a plumber
  
   to investigate further.

Taking off the toilet tank top:

Some of these simple toilet diagnosis steps require that you look into the toilet flush tank on the back of the toilet.

Just lift the top off of the toilet tank and set it carefully aside on the floor where you won't break it or trip over it.

If you leave the tank top on the toilet seat (as we did for this photo) you're asking for trouble, and also, it's a bit in the way. 

Our sketch below shows the parts you'll see inside the toilet tank. You may want to refer back to this drawing while reading the details of each class if individual toilet problems listed above and how they are detected, diagnosed, and repaired.

Tank reservoir toilets like the toilet in the sketch and in our photo just above, have been in wide use in North America since the 1940's.

While there have been improvements in toilet tank fill valves, flush valves, floats, and water savings, the design has remained about the same.

[Click to enlarge any image]

A flush lever moves an arm to lift a flapper valve or tank ball to permit water to rush into the toilet bowl below, washing away waste into the sewer pipe.

At the end of the flush cycle, a float arm, or a float moving on a vertical stalk (newer valves) drops to open a valve permitting the toilet tank to refill with water.

When the toilet tank water level reaches the proper level, the float closes the toilet tank fill valve.

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2019-10-31 by quinn

Water seems to leak into toilet bowl causing flushing

This Q&A were posted originally at TOILET REPAIR GUIDE - home

On 2019-10-31 by (mod) - water leaks into toilet bowl causing the toilet to flush itself

Quinn

When a toilet seems to flush itself without being asked there is a water leak from the tank or cistern down into the bowl. Eventually enough water leaks out of the cistern and into the bowl that the water level in the cistern drops enough that the toilet fill valve opens to re-fill the toilet.

The most-common leak point is the flapper valve or flush valve. That's something easily replaced by the homeowner on most toilets and it's inexpensive. Take a look in the toilet tank, buy a new flapper valve, remove the old one, clean off the opening edges against which the valve seats (I use a scrubby sponge), and install the new valve, connecting its pull chain to the flush arm lever.

If the flapper valve is NOT leaking or if after replacing it the problem continues, it's possible that the whole flush assembly in the center of the cistern is leaking around its base and into the toilet.

Replacing the toilet flush valve seat assembly is a bigger job as one has to turn off water to the toilet, disconnect the toilet water riser supply pipe from the bottom of the tank, unbolt the tank, remove the center flush assembly, and install a new one with new gasket.

This sounds more intimidating that it ought as a homeowner who's familiar with an adjustable wrench and screwdriver is usually up to the task;

Building suppliers like Lowes or Home Depot sell repair kits for both of these repairs, made by Fluidmaster and other vendors. The kits include illustrated, detailed instructions.

Watch out: What can go wrong? The worst snafu would be a toilet water supply valve that won't shut off.

So before undertaking this repair I would turn off water to the toilet, then flush it, and observe that no new water is entering the tank or cistern.

If no water's re-filling the tank then hurrah, the shutoff works and we can proceed with the repair.

Question: can't find the cause of a running toilet

(Apr 24, 2014) Anonymous said:
My toilet ran all the time. I fixed it by installing new inner workings. (valve?). Then it started again......running all the time with low water pressure and slow recovery time. Now all the rest of the house has low water pressure. Is there a connection? thanks, Bridget

Reply:

Bridget, you want to look very closely at where the toilet is losing water. Even if the fill valve is in perfect shape, if the toilet fill level is adjusted wrong it will overflow into the overflow tube into the bowl, OR you could have a leak at the gaskets between the toilet tank and the bowl.

Try turning off water into the toilet entirely. Then pour some food coloring (I use septic test dye) into the toilet tank. Now watch the bowl. If you see the colored water entering the problem is a leak.

A repair kit for toilets can replace the bolts and gaskets between tank and bowl.

Also review our notes above about running toilet leaks at the spud gasket.

On 2016-08-14 by (mod) -

Excellent; glad you were able to find and fix the trouble.

Indeed sometimes a leak at the toilet flush valve can be a devil to find and fix: the flapper itself may leak slowly, or as you found the leak could be at the mounting gasket below the flapper-valve seat

. I've also found on some toilets, leaks at the bolts mounting the tank to the toilet base. Usually those leak onto the floor, but not in all toilet designs.

On 2016-08-14 y Doug

Thank you for the dye test. Dye was going into bowl. Replaced flapper gasket and no more dye in bowl.

On 2016-01-24 by (mod) - toss a working Bic lighter in the toilet tank?

A flame could ignite sewer gases and cause an explosion.

Watch out: such an explosion could cause fire, injury, death. However it's pretty unlikely - only if a toilet bowl were completely dry could sewer gases easily re-enter the building from the sewer piping. Even then the gases would be in the toilet bowl and general bathroom area, not specifically in the toilet tank or cistern.

Watch out: while it is rare, in some communities natural gas leaks into water wells can send combustible gases through the water supply system. At

Methane gas in well water: in WATER POLLUTANT SOURCES from the U.S. EPA cites and we elaborate that methane gas or musty/earthy smell in water may be from decaying organic matter in water.

[or from direct methane gas leaks into aquifers and water wells. We've had reports, especially from mining areas such as portions of Pennsylvania in the U.S. in which underground methane was seeping into the well through rock fissures.

On 2016-01-19 by Jean

This is a serious question! Why would a person intent on causing damage toss a working Bic lighter in the toilet tank? What can this do?

On 2015-12-31 by (mod) -

Check the flapper pull chain length - it may be too short.

On 2015-12-31 by AL

Toilet flushes, but the tank drin flapper does not close

...

Continue reading  at TOILET TANK SWEATS - condensation may also indicate a running toilet, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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