Toilet running causes stains in bowl (C) Daniel FriedmanRunning Toilet Repair Guide - How to Diagnose & Repair a Toilet that Runs

  • TOILET RUNS CONTINUOUSLY - CONTENTS: Running toilet repair guide: how to diagnose and fix running toilets. How to diagnose and fix toilet noises. Why a running toilet can ruin a septic drainfield. Toilets that keep running - fill valve does not shut off the toilet tank fill valve?
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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 TOILET REPAIR GUIDE 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.

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Toilet Runs Continuously - Diagnosis & Repair

Stained toilet bowl indicates a running toilet (C) Daniel FriedmanIs your toilet running? Better go catch it! 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.

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

Condensation on toilet tank (C) Daniel FriedmanA 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.

  • 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.

Vertical float toilet fill valve (C) Daniel Friedman
  • 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.

Toilet flapper valve in use (C) Daniel Friedman
  • 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 (left) 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.

    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.

Toilet tank parts (C) DanieL Friedman
  • 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.

    If leaks are at the toilet tank mounting bolts you will probably see water on the floor.

    [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.

    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.

Toilet with tank lid on seat(C) Daniel Friedman

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.

Toilet tank parts (C) DanieL Friedman

Tank reservoir toilets like the toilet in the sketch at left 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.

Here is our list of toilet trouble diagnosis and repair articles. You will see that some toilet problems are fixed easily and right at the toilet by a simple adjustment, while others may not be the toilet's fault at all, and may need more thoughtful diagnosis and repair.

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