In Repair & Maintenance

How to Fix a Running Toilet in a Few Easy Steps

As an Amazon Associate, I earn from qualifying purchases. See my disclosures for more information.

There is nothing more frustrating than a running toilet. You can waste hundreds of dollars in water and it makes annoying noises constantly. Believe it or not, it’s actually not difficult to fix a running toilet. All you need to fix a running toilet, depending on the problem, is a screwdriver, some gloves, toilet parts, silicone caulking, a bucket, and some rags.

What You’ll Need to Fix a Running Toilet


  • Multibit Screwdriver
  • Long Rubber Gloves
  • Toilet Parts (Fill valve, Flapper, etc)
  • Silicone caulking
  • Bucket
  • Rags

How a Toilet Works

how does a toilet work
Image credit: Landmark Home Warranty
  1. Water enters supply line from valve in wall
  2. Water runs through the fill valve
  3. Flapper closes as flush lever is released
  4. As tank fills up, float rises
  5. Float reaches the top of the fill valve
  6. Fill valve shuts water off

In order to fix your running toilet, you’ll need to first understand how a toilet works. There are really only a few key components to a toilet fortunately. One thing to note is that your float could be part of the fill valve or it could be a separate balloon shaped piece, depending on which type of toilet parts you have.

At its most basic, water flows from a supply line through the fill valve until the float reaches a specified point. Once the float reaches maximum, the fill valve shuts off. The flapper is a large rubber seal at the bottom of the tank that lifts up when the toilet is flushed. 

This allows all the water in the tank to rush into the bowl and down the drain. If there is more water in the tank than there should be, the overflow tube allows extra water to drain into the bowl so the tank doesn’t overflow.

Diagnosing Why Your Toilet is Running

There are a few key areas that could need attention if your toilet won’t stop running. Each one is simple to diagnose. Before you begin to diagnose your running toilet, take the lid off the tank and watch it flush once. 

Look for water flowing after the flush sounds like it’s stopped. Look to see if water is running into the bowl or into the overflow tube. If you still can’t tell what the problem is, turn the supply line off by turning the knob on the wall clockwise until it stops. DO NOT crank it too tight, just tighten it down with your hand.


two types of toilet float

If you have a float ball, the ball itself can go bad over time. Take the float ball off of the arm it’s attached to, by unscrewing it counterclockwise, and look to see if there is any water inside of it. If there is water inside of the float ball or cracks in the float ball, you need to replace it with a new one.

If your float is integrated into the fill valve tube, you can’t remove just the float to check it for leaks. You’ll have to replace the entire fill valve assembly. One good indicator that something is wrong with your float is if water continues to flow and flows into the overflow tube after the flush is done.

Flapper Valve

The flapper valve is a large piece of rubber attached to a large piece of plastic at the bottom of the toilet tank. This rubber can go bad over time and get cracked or warped. First, look to see if the flapper valve has any obvious missing, warped, or cracked areas. 

If you don’t see any obvious signs of damage, try pulling up briefly on the chain attached to the flapper valve. Once water is flowing, let the chain go and see if the flapper valve stops the water flow. If it does not shut down the water flow within a few seconds, the flapper valve should be replaced.

Fill Valve

The fill valve of a toilet could need to be replaced if the bottom washer is deteriorated or if the fill valve is clogged with hard water minerals. If the bottom washer is deteriorated, you will notice water leaking down the supply line going into the wall. This is something you should be able to diagnose without turning the water off.

Even with a water softener, your fill valve can get clogged with minerals and deposits!

If the fill valve is clogged with minerals, you will notice a couple of things. First, the water won’t come into the toilet with a steady flow but instead trickle in and take a long time to fill the tank. Also, your float will have trouble moving to shut off the water. This will lead to the toilet overflowing into the overflow tube.

Instructions to Fix a Running Toilet

Once you’ve figured out why your toilet is running constantly, you need to fix the broken part. If you still haven’t been able to determine the broken part, there are complete kits that you can buy with every part of the toilet mechanism inside. 

9 steps to fix a running toilet

A great option is one from Korky because it’s a relatively universal kit and they supply a helpline if you get stuck that is invaluable in getting your running toilet repaired. It isn’t that much harder to replace all of it than one part so don’t hesitate to do so.

Once you are ready to replace your toilet mechanism, turn the supply line off and flush the toilet a couple of times to drain the tank as best you can. For the last little bit of water, you’ll need to pull the flapper chain up manually. You’ll never get the tank 100% empty so put a bucket and some rags underneath the fill valve side to catch any drips.

If you Keep Having Water go into your Overflow Tube

how to extend a toilet overflow tube

Your overflow tube may be set too low compared to your float. Raise the height of the overflow tube to correspond correctly. Most of them work like a shower rod, turn them one way to loosen them, separate the two parts, turn the other way to tighten them. 

Once you have the overflow tube set to the right height, turn the supply line on to see if water shuts off before going into the overflow tube. If it doesn’t, and the overflow tube is at a good height (level with the float valve) the issue is the float valve.

If you need to replace your float so that the water shuts off appropriately, remember that you may have to just replace the ball on it or the whole fill valve. If you have a ball float, it’s a simple matter to replace it using the same method you used earlier to check it for cracks. If you have an integrated float, you’ll need to replace the whole fill valve.

If the Issue is the Flapper Valve

If your running toilet is the result of a deteriorated flapper valve, you need to take a couple of things to the hardware store to make sure you get the right one. Take the old flapper valve if you can by loosening the two screws that hold the plastic on.

Take the following to the hardware store with you:

  • Brand of tank
  • Brand of toilet
  • Old flapper valve

You should also prepare for the hardware store by knowing which brand of toilet and which brand of tank you have. They don’t always match. Each brand has a different flapper valve connection and it is vital that you match your new flapper valve with your tank.

8 steps to replace a flapper valve

Once you have your new flapper valve, unscrew the current one if you haven’t already. The easiest way to do this is to make sure the tank is as empty as you can get it and then use a multi bit screwdriver to take the screws off the existing flapper. Once you have the flapper loose, remove the chain connected to it and remove the old flapper.

Install the new flapper valve by gently putting it between the seat arms on the toilet tank. Screw the screws into the plastic, reattach the chain, and test it a couple of times by pulling up on the chain manually. Turn the supply line back on and do a few test flushes to make sure that the new valve works well.

If the Issue is the Fill Valve

You may find that you have a running toilet because the fill valve has gone bad. Look for signs of mineral build up. No matter what type of fill valve you have, if your water only trickles out or comes out slowly regardless of what the supply line is set to, that’s a good sign of mineral build up.

Also look to make sure that the float can actuate correctly. If the float doesn’t seem to operate along its full range of motion, it’s probably clogged with minerals. When the float can’t go up the whole way, the fill valve won’t turn off. In both types of toilet mechanism, this means replacing the fill valve.

8 steps to replace a fill valve

To replace your fill valve, turn the supply line off and drain the tank just like if you were replacing the flapper valve. Carefully loosen the nut on the bottom of the tank on the fill valve side. This is the nut that connects to the bottom of the fill valve and once it’s loosened, you can pull the fill valve out.

Insert the new fill valve, the washer that came with it should be underneath the fill valve and on the inside of the tank. Tighten the nut on the outside of the tank to secure the fill valve. Set the valve according to the instructions it came with, each one is different, and turn the water on to test it.

Will a Running Toilet Eventually Stop

No. The only way to stop a running toilet is to replace the broken mechanisms or to turn the water off. Turning the water off is not a desirable solution unless you don’t want to use that toilet anymore. Identifying and replacing the broken mechanisms, as you can see, is not difficult.

Is a Running Toilet an Emergency

Despite how annoying it is, a running toilet is not an emergency. You can go for months, even years, with a toilet running constantly. Because of this, plumbers probably won’t put you at the top of their list to fix when they’re busy. But you can fix your running toilet by following the steps here.

How Does a Running Toilet Affect your Water Bill

A running toilet will cost you hundreds of dollars in wasted water if you let it continue for a long time. It starts with a drip here and there but those drips add up over time to thousands of gallons. Because of this wasted water and money, a running toilet should be fixed as soon as possible.


Fixing a running toilet is something that every new homeowner is going to have to do at some point. It’s a great project for those homeowners who are somewhat familiar with plumbing but not incredibly experienced.

Once you figure out what the problem is and which mechanism or valve needs to be replaced, fixing a running toilet is fairly simple. Don’t hesitate to try it yourself and see what you’re capable of.