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Why is my toilet running constantly?

The sound of a constantly running toilet is annoying at best, and can signal the waste of hundreds of gallons of water at worst. Luckily, there are some basic ways you can troubleshoot and even fix the problem — bringing some peace and quiet to your bathroom and helping save the planet at the same time.

How a toilet flushes

Before attempting to diagnose and fix a toilet problem, let’s understand the mechanics of a toilet. A toilet works because of gravity. Residential toilets hold water inside their tank until someone depresses the handle, which lifts a tank ball or flapper away from the flush valve, which allows the water in the tank to cascade into the bowl and start the siphonage action that evacuates the contents of the bowl. The tank ball or flapper reseats itself on the flush valve outlet, and water begins refilling the tank. An afterfill tube sends a stream of water down the overflow tube to refill the bowl. The ball cock valve is adjusted to add water until reaching the marked water level required for proper flushing. 

Common causes of a running toilet

A broken or leaking flapper. If water is running intermittently but not flowing to the overflow tube, the toilet flapper probably needs to be replaced.  Your typical toilet tank has a flapper that seals the water in the tank. When you flush, the chain attached to the flapper raises it up and allows water to go into the bowl. Once enough water exits the tank, the flapper drops back down, re-sealing the tank. However, if the flapper (or the valve seal) is broken, it will slowly drain the tank and seep into your toilet bowl, causing it to run constantly.

A toilet fill valve issue. Even though a running toilet is often caused when the flapper is leaking, it can also be because the fill valve has become worn out. If water is constantly running into the tank and into the overflow tube, the toilet fill valve is probably the issue. The fill valve fills the tank after each flush. You can test the toilet fill valve by lifting the float ball to see whether the water stops.

The float is too high. When a toilet continues to run after the flush cycle is completed, it might be because the water level is too high in the tank. By bending the float arm downward, the float ball will shut off the water at a lower tank level. Adjusting the water level in the tank is a matter of “fine-tuning” the point at which the float ball shuts off the valve. 

Tools required

Now that you have some ideas of what the issue is and how a toilet fundamentally works, it’s time to gather some tools. Luckily, the tools you’ll need are probably already in your house:

  • A 4- or 6-way multipurpose screwdriver (a versatile screwdriver with interchangeable bits of common sizes)
  • Adjustable pliers
  • A small adjustable wrench
  • A flashlight

Repairing or replacing a fill valve

  1. Use a screwdriver to adjust the spine that runs along the side fill valve.
  2. Turn it counterclockwise to lower the float cup and the water level so it stops below the overflow tube.
  3. Fill valve kits include a metal clip or angle adapter that will prevent the refill tube from going below the waterline. If the refill tube is pushed down into the overflow tube, it will cause the tube to constantly siphon water from the tank. 
  4. The refill tube should be attached to the angle adapter clip and sit right above the overflow tube (not inside the tube).

Repairing or replacing a flapper

  1. Turn off the water supply at the shut-off valve (usually in the basement or on an outside wall in a utility area of the house). Turning off this valve (by turning it clockwise) cuts off the water supply to the entire house. Then flush the toilet multiple times until all the water has drained from the tank. Pro tip: Use a large sponge to soak up the remaining water at the bottom of the basin and squeeze it out into a bucket.
  2. Reach into the tank and gently remove the flapper by pulling it off the two studs on both sides of the flush valve.
  3. Remove the chain from the flush handle lever.
  4. Install the new flapper by threading the holes on each side, over the two studs.
  5. Attach the chain to the flush handle lever, but make sure not to pull the flapper open in the process.
  6. Turn on the water supply by turning the shut-off valve counterclockwise and flush the toilet to make sure the leak is fixed.
  7. If the flapper doesn’t close properly, adjust the flapper chain length as needed.

Time and cost of a DYI repair

For a do-it-yourself job, you can expect to spend anywhere from $15 to $150 in parts, and it will take about an hour. Keep in mind that if your toilet or its parts are cracked or chipped, or if it has severely fouled rim jets or siphon jets, it may be time to replace the whole toilet.

To replace a whole toilet could take several hours.

Get a remote diagnosis from ANEW

If a home repair is unsuccessful and the toilet continues to run, the underlying issue may be more complex, such as wrong parts or an incorrectly adjusted tank ball, flapper or ball cock valve.

You might want to consider hiring a professional. ANEW offers an easy, efficient and affordable repair service with remote diagnosis for just $20.

Get answers with Anew

Video chat with an expert to pinpoint your home’s issues remotely, then get it repaired fast with Anew’s DIY or Professional solutions.

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Get answers with Anew

Video chat with an expert to pinpoint your home’s issues remotely, then get it repaired fast with Anew’s DIY or Professional solutions.

Get Started

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