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Why Does My Toilet Keep Running? | 5 Solutions

water flushes in toilet bowl

According to David Balkan, the CEO of Balkan Sewer & Water Main Service in NYC, a running toilet can waste up to 200 gallons (757 liters) of water daily, adding ~$3 to the water bill per day. If you have a toilet that keeps running, you must identify the cause and fix the problem asap. 

The common reasons why a toilet keeps running are a high float, a defective fill valve, a failing flapper due to grime and mineral buildup, a dangling or short chain, etc. Raise the float, replace the fill valve or flapper, and check the chain, flush lever, and overflow tube.

In most cases, a running toilet has only one problem, but whether you can fix it instantly or the malfunctioning component needs to be replaced depends on your inspection and what you find. Keep reading to inspect why your toilet keeps running and choose one of the relevant solutions.

5 Reasons Why My Toilet Keeps Running

Standard toilets have the following components inside the tank:

  • A flush lever or rod extending from the handle
  • A flapper chain connected to the flush lever
  • A rubber flapper at the base of the toilet tank
  • A float, also known as a float valve or ballcock
  • A fill valve assembly with the float and refill tube
  • An overflow tube with the flush valve assembly

All these internal components have mechanical functions. If any part doesn’t operate as it must, your toilet may keep running depending on the specific malfunction. Here are the 5 reasons why your toilet keeps running:

The Adjustable Float Is Too High

The water supply line fitted to the toilet tank is connected to the fill valve assembly inside. All fill valve assemblies in standard toilet tanks have a float. This float is adjustable, regardless of its shape and type, so that you can regulate the water level in the tank.

If the adjustable float is set too high, the fill valve will allow surplus water to flow into the tank. As the water in the tank rises above the critical level, it will flow into the overflow tube and down to the toilet bowl. Unlike the flapper that you open while flushing, the overflow tube doesn’t have a stopper or valve that you can regulate. Excess water will continue to flow into the toilet bowl.

The fill valve doesn’t shut the water supply to the tank in such circumstances because the float is too high. So, a toilet tank with a continuous water supply will have the excess flowing down its overflow tube and into the bowl.

The Flapper Chain Has No Slack

If no water is flowing through the overflow tube into the bowl, a running toilet may be due to an open flapper. The rubber flapper at the base outlet of the toilet tank may stay open if you have a short or taut chain. This chain connects the flapper to the flush lever and tank handle.

A short or taut chain can prevent the flapper from closing completely after you flush the toilet, so the tank might continue to leak water, and it may never get full until you fix this leakage.

The Flapper Is Bad, Dirty, or Open

Suppose you don’t have a short or taut flapper chain. Even then, the flapper may stay open with a blocking or tangled chain. A long chain can get stuck between the flapper and the outlet of the tank after you flush. A stuck chain prevents the flapper from closing completely as the tank fills.

If the chain is fine, you may have a bad or dirty flapper, and probably both in some cases. Any old flapper may be dirty with a substantial buildup of grime and mineral deposits that can keep it open after a flush. Also, a defective or deformed flapper can leak, causing a running toilet.  

The Fill Valve Assembly Is Defective

One of the most common causes of a running toilet is a defective fill valve assembly. This is the part inside the tank, usually towards the left side if you are facing the toilet, that has the hose or water supply line connected at the bottom. Suspect the fill valve after you check the float’s level.

Suppose the float valve or ballcock is at a sufficient height below the critical level of the overflow tube. Still, the tank has excess water rising and flowing through the overflow tube, which causes the toilet to keep running. The fill valve assembly is defective and not shutting in such a case.

A defective fill valve doesn’t require any other component to fail or malfunction to cause excess water to flow into the tank. This continuous or unchecked supply will cause an overloaded tank to have the excess water naturally flow into the overflow tube and down to the bowl.

Check Overflow Tube and Flush Lever

A short overflow tube isn’t usually a problem for a running toilet unless the original component is cut during installation or you replace the old one with an incompatible size. Even if this tube is a bit short, adjusting the float to be below the critical level should prevent an overflow.

However, it is worthwhile to check whether or not the overflow tube is a little shorter than ideal if the float valve wasn’t adjusted or the buoyant component appears alright. An extremely lowered float or ballcock will shut the fill valve before the tank has sufficient water for a proper flush.

Like a short overflow tube, a misaligned flush lever isn’t a typical cause of a running toilet. If the flush handle outside or the rod inside is bent or deformed, it will be evident, and you’re likely to encounter one or more of the following symptoms:

  • Flushing issues
  • Malfunctioning flapper
  • Unusual chain tension

However, if you have a deformed or misaligned flush lever or rod, the part may wobble or work abnormally while you flush. The ineffective action on the chain and flapper may cause those two components to fail or malfunction.

5 Solutions To Fix Your Running Toilet

Installation of water-saving toilet

Prioritize the first 4 problems I have explained above to detect the reason why your toilet keeps running. Once you identify the cause, opt for the corresponding solution among the following. If you have a rare situation of two or more causes, you must address both or all of those issues.

1. Lower the Float’s Level in the Tank

Most standard toilets have one of the following types of adjustable floats:

  • A buoyant ballcock extends from the fill valve assembly on the left of the tank to the right. This ball floats as the water level rises when the tank fills and shuts the supply valve when it reaches the set alignment with the assembly.
  • An adjustable float, usually cuboidal, with a valve inside, attached to the fill valve assembly. Unlike the ballcock, this type of float doesn’t extend sideways a lot from the fill valve assembly across the tank. The float is on the fill valve assembly.
  • Some fill valve assemblies have an internal float valve, usually somewhere at the top. This type of valve is also adjustable to lower or raise the target water level in the tank.

If your toilet tank has a ballcock, the arm extending from the fill valve and the float ball itself will lower as you adjust the screw. A box-like float and valve will also go down or rise up as you use the screw to adjust its height. In either scenario, let the tank fill and check if the fix has worked.

2. Check the Flapper Chain and Fix It

The flapper chain inside a toilet tank should have a slight slack, neither dangling and loose nor too tight. You can easily loosen or tighten the chain by toggling the hook and the links. Take the hook off the flush lever, wind a few links, and reassemble the chain if it is too loose.

If the chain is too short or tight and keeps the flapper open, take the hook off, extend or unwind a couple of links, and test the new assembly by filling the tank and flushing the toilet. Extending or unwinding the flapper chain by working on its links and the hook is a straightforward process. 

3. Replace a Damaged or Old Flapper

You can clean a dirty flapper if it has grime and mineral deposits. If cleaning the flapper closes it completely and fixes a running toilet, you don’t have to replace the rubber seal. Otherwise, you should match the flapper you have to get an identical or compatible one as its replacement.

Standard flappers are attached to the flush valve assembly, which includes the overflow tube. A flapper may have ears mounted on the pivot arm of the overflow tube, or it can also have a ring that glides down over the flush valve assembly, and you secure it at the base with the hooks.

Don’t get a universal flapper without matching it with the one you have. Removing your flapper will help you to understand how you will reinstall it, so the new one you get should have identical features. Always shut off the water supply valve below the toilet before you work on the flapper.

4. Replace a Bad Fill Valve Assembly

If you have a bad fill valve assembly, you have to replace it with an identical or similar one. It is possible to clean and repair some fill valves, but the effort and time are not worthwhile. Besides, a new fill valve is likely to be inexpensive.

Always shut off the water supply valve before you access and check any of these internal parts of a toilet tank. Match the fill valve part number or type you have to buy a new one. The steps to install a new fill valve may vary, but here is the generic process:

5. Change Overflow Tube or Flush Lever

A deformed or misaligned flush lever is an evident problem. Replace it if the flapper or its chain doesn’t work properly after or when you flush. Likewise, an overflow tube’s size isn’t a common issue, but replace a short one if the float height has to be lowered to an unviable extent.

  • After you shut the water supply line, flush the toilet, and remove the hose from the toilet tank by unscrewing its locking nut. Place a bucket or towel under the toilet tank for any residual water inside the hose and the fill valve or refill tube.
  • Disassemble the old fill valve assembly by unscrewing its mounting nut under the tank. You may need an adjustable wrench or spanner to remove the nut. If the assembly has a float ball, you can remove it from the extended arm before removing the fill valve.
  • Insert the new fill valve assembly into the hole of the tank and secure it with the mounting nut. Set the height of the refill tube at ~1 inch (2.5 cm) above the overflow tube. Set the adjustable float height at ~1 inch (2.5 cm) below the overflow tube’s critical level.
  • Reconnect the water supply hose and secure it with the locking nut before turning on the line shut-off valve. If you had removed a float ball from the extended arm, put it back on the new fill valve assembly before opening the shut-off valve.
  • Check for leaks and if the toilet keeps running. Tighten the connections if there is any leak under the tank. Adjust the float height and the level of the fill tube if the toilet is still running.


Check the adjustable float height and if the flapper is closing completely after you flush a toilet that keeps running. Inspect the flapper chain to ensure it isn’t keeping the seal open. Suspect the fill valve assembly if the flapper, float height, or flush lever chain isn’t the problem.

Tags: DIY, plumbing, toilets

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