How To Fix A Toilet That Runs Constantly After Flushing

As your toilet ages, it is normal for rubber or metal component parts to wear, rust, or degrade over time. It is this degradation that causes your toilet to run after flushing. Excess water usage drives up your water bill, and the sound of water running has the potential to drive you crazy. 

The good news is that this issue is usually easy to diagnose and simple enough for you to fix yourself without calling out a plumber. It just takes a basic understanding of how a toilet operates and a little DIY know-how to stop your toilet from running after you flush it.

The worn component part that is likely causing the issue is either the flush valve assembly or the fill valve assembly, both of which are easy to adjust or replace. 

The important thing to remember when searching for replacement parts is to make sure you get compatible parts. Not all toilets are created equal, so you’ll need to know the brand and model you have so you get the right parts. With that said, if you aren’t familiar with do-it-yourself plumbing projects, replacing these parts may seem a bit challenging, but taking the time to learn and understand how a toilet works will enable you to identify and repair the issue yourself. Let’s get started with a short lesson on toilet functionality. 

Basics of How a Toilet Works

I am sure that you already know that a toilet tank fills with water, and when flushed, the water leaves the tank and flows into the bowl, to flush the waste down the drain and out of your home. But let me explain exactly what happens inside the tank to make the toilet work. 

Water enters the toilet tank through an inlet pipe called the fill hose, which is attached to the fill valve. As the tank fills with water, a ball float or float cup sits on the surface of the water and rises with the water level. When it reaches a predetermined level, the float mechanism automatically closes the inlet valve and stops the incoming flow of water. 

If the fill valve is faulty, the water could continue to rise and spill into an overflow tube. The overflow tubes’ job is simply to allow water to run off into the bowl, as opposed to building up in the tank and potentially leading to flooding. 

The water held in the tank is sealed in by a small device called a flapper – a round rubber stopper located at the bottom of the tank. The flapper opens or closes with each flush to either trap water inside the tank or allow water to flow out into the bowl. 

When you push the flush handle or button, you engage a rod that pulls a chain to lift the flapper, effectively opening it. This action allows water to flow out of the tank into the toilet bowl through small holes located around the rim of the bowl, called rim jets. Sometimes, a toilet will have an extra water inlet called a siphon jet that allows for an even stronger water flow.

As the water level in the toilet bowl rises, the waste and wastewater are forced out through the S-trap and out into your home’s main drain line. Finally, the flapper in the tank closes, creating a watertight seal, and the tank begins to fill with water once again. 

Why Your Toilet Keeps Running After Flushing

How a toilet works aren’t complicated, but there are a few parts that can wear out and cause frustration when the toilet keeps running after flushing. You will need to troubleshoot the problem to find out exactly what’s causing the issue before you can make the appropriate repairs that’ll keep your toilet from running constantly in the future. 

When a toilet continues to run intermittently or constantly after being flushed, it’s usually one of three parts causing the problem: 

  1. The overflow tube
  2. The flush valve assembly
  3. The fill valve assembly

You’ll want to start by checking the water level in the tank. If it is too high, you may need to adjust it. It’s possible that the overflow tube is too short for the toilet, in which case, you’ll need to replace the flush valve assembly. 

If the water level is correct (about an inch below the top of the overflow tube) and the overflow tube is the right height for your toilet, the fill valve is likely to be causing the problem. 

On the other hand, if the water is not flowing into the overflow tube and you still hear the toilet running after the flush cycle is complete, it could be an issue with the flush valve assembly. The chain that operates the flapper could be too short, preventing it from closing and sealing. Or the flapper itself could be warped or covered in mineral deposits, or the rubber seal may be breaking down, all of which can cause water to seep into the bowl when it shouldn’t.   

Fixing a Running Toilet  

Besides being annoying, a constantly running toilet will increase your water bill each month. In today’s environmentally-conscious world, wasting water in this manner is bad news and it should be addressed sooner rather than later. 

Follow the steps below to identify the issue and make the necessary repairs that will stop your toilet from running randomly after flushing. 

1. Inspect Overflow Tube Height 

The first place to start is to check the overflow tube height. The overflow tube is part of the flush valve assembly and should stand about an inch or so above the water level. 

Check to see if the water level is high or level with the top rim of the overflow tube, causing the runoff of water into the overflow. 

It’s possible that the overflow tub may have been cut too short during installation. If the overflow tube is too short for your toilet, you will need to replace the entire flush valve assembly. If the overflow tube seems to be the right height, move on to the next step. 

2. Check the Water Level and Float Position

If you’re sure the overflow tube is the correct one and it wasn’t cut too short during installation, the water level in the tank may be too high. You can lower the water level by adjusting the float. 

Some toilets have a float rod and float ball, while others have a float cup. Either way, locate the screw that allows for adjustment and turn it a quarter turn counterclockwise. 

Flush and check the water level. Continue to make quarter-turn adjustments until the water level stops an inch below the top rim of the overflow tube. 

If, after making this adjustment, your toilet continues to run after flushing, the problem is most likely the fill valve or the flush valve – so continue to the next step. 

3. Check Flapper Chain is Functional

If your toilet keeps running but isn’t spilling into the overflow tube, the issue might be with the flapper chain. Remember, the flapper chain raises the flapper when you push the flush handle or button. If this chain is too short, it won’t let the flapper close completely, allowing water to constantly seep into the bowl.

If, on the other hand, the chain is too long, it can become trapped underneath the flapper, again, allowing water to flow into the bowl when it isn’t supposed to. 

With the tank cover off, flush the toilet and watch the flapper. Does it close completely? If the chain is too long, remove a couple of links to shorten it. If it’s too short, you will need to purchase a new chain to stop your toilet’s constant running. 

4. Check Flapper or Flush Valve Seal

The flapper is made of rubber, which can deteriorate over time. When this happens, it can warp or crack, which will cause the flapper to leak. In some instances, especially if you have hard water, the flapper can become caked with mineral deposits that can stop it from creating a watertight seal.

Check the flapper itself to determine if either of these scenarios looks to be occurring and replace the flapper if needed. 

5. Replace The Flush Valve

If, after checking all other possible causes above, your toilet still runs after flushing, the problem could be a faulty flush valve assembly. 

To replace this part, you will need some channel locks and a helper as you will need to separate the toilet tank from the bowl, and the tank is heavy!

  • Begin by turning off the water supply by turning the inlet valve all the way counterclockwise. Flush the toilet to empty the water from the tank, and then use a towel or sponge to remove any remaining water in the bottom of the tank.
  • Detach the water supply hose and place the end in a bucket or cup to prevent spills.
  • Next, remove the bolts that hold the tank onto the bowl. Have someone help you carefully lift and separate the tank from the bowl. 
  • Remove the gasket that rests between the tank and bowl and then remove the old flush valve assembly. It will have water inside, so place it in a bucket or sink to prevent spills. 
  • Install the new flush valve assembly by tightening the nut and replacing the gasket before placing the tank back on top. 
  • Tighten the bolts that hold the tank on and reattach the water supply hose. 
  • Turn the water back on and wait for the tank to fill back up. 
  • Check for leaks at the bottom of the tank. rand

If your toilet continues to run after the tank fills, and there are no leaks that you can see, the gasket between the tank and bowl might be damaged or the flapper might not be installed properly. 

6. Replace The Fill Valve 

Sometimes the water in a toilet tank will continue to spill over into the overflow tube even when the tube is the right height for the toilet. This happens when the fill valve is faulty. If this is the case, you will need to replace the fill valve, which is easier than replacing the flush valve assembly. 

  • First, turn the water off behind the toilet and flush it to drain the water from the tank. Use a sponge or towel to remove any excess water that didn’t drain. 
  • Remove the water supply hose from the fill valve, and then remove the old fill valve by loosening the lock nut. 
  • Install the new fill valve, making sure to adjust the valve and float to the appropriate water level. 
  • Tighten the lock nut to secure the fill valve and reattach the water supply hose. 
  • Turn the water back on and check for leaks. 

If the repair is done correctly, the water will stop filling as soon as it reaches the pre-set level. 

When to Contact a Plumber

As an avid DIYer, you may be experienced in many areas of home improvement. For instance, you may have completed your fair share of landscaping or woodworking projects, and that’s very admirable. However, if you haven’t done much plumbing work or don’t feel comfortable tackling such a project on your own, by all means, contact a licensed plumber to fix your running toilet. 

Hiring a plumber might cost more, but it’s worth it knowing that your toilet will be fixed safely, quickly, and correctly. You won’t have to worry about things like cutting the overflow tube too short or dealing with a leaking toilet tank.

Of course, if your toilet continues to run after exhausting all the steps above, calling in a trained professional is your last option. A reputable plumber will be able to troubleshoot the issue quickly and get your toilet back up and running in no time.

You may be interested in reading Is Your Toilet Making A Hissing Sound | Fix It

Toilet That Runs Constantly After Flushing

Will a running toilet eventually stop?

No, a running toilet will not stop on its own without some sort of intervention. A running toilet is usually caused by an issue with the flushing mechanism, such as a damaged flapper or a faulty fill valve, that prevents the toilet from filling and shutting off properly.

Plumber and HVAC Technician | Website | + posts

As a retired Master Plumber Jamie has over 30 years of hands-on experience, making his plumbing knowledge second to none. He has also worked on both residential and commercial HVAC installation and repair projects.