Stop a Running Toilet DIY Guide

Have you ever been in a situation where the water in your toilet continuously runs, even if you haven’t flushed for a while? You’ll know your toilet is running if you can hear the water moving through it even when it’s not in use or hasn’t been used recently. While a running toilet may not seem like a serious issue, it can cause several problems in the future.

Further, running toilets impact your toilet’s flush strength and even water consumption. Follow this article to learn how to fix your running toilet to improve your toilet’s flush, lower your water bills, and avoid larger problems in the future.

What Happens When You Flush

Let’s start by getting background information on how your toilet works when it’s functioning like normal. So, what happens when you flush a toilet?

  1. To initiate a flush, you’ll press to activate the flush lever on the tank.
  2. Once pressed, this lever opens a valve (or flapper) which is the internal part that causes the cistern to empty into the bowl through the part called a siphon.
  3. Next, water flows through holes in the rim and clears the bowl.
  4. If the toilet works properly, there should be enough water to reach the S-trap (an area below the hole in the bowl, creating a siphon effect that sucks any waste from the bowl down the main drain.
  5. As water empties from the tank, the float falls and tilts the lever.
  6. This lever opens the ball valve at the base of the tank, and when the float reaches the correct level, the valve switches off the water supply.

How to Stop a Toilet from Running –  4 DIY Steps

Now that we’ve run through how your toilet should function without any issues, let’s address what to do when you’re faced with a running toilet. First, let’s see what tools and materials you will need. You’ll want to make sure you have the necessary tools and equipment before you start working so you won’t need to stop and go to the store partway through the task.

Tools required:

  • Pliers
  • Cutting pliers
  • Gloves

Materials required (depending on issue):

  • Fill valve
  • Toilet flapper

Note that you might not need to have both the fill valve and the flapper, since it depends on the problem. However, you can’t go wrong by getting both since they are quite affordable.

You may be interested in our informational guide about canister flush valves vs. flappers.

1. Check the Fill Tube

One cause of your issue could be the overflow tube. First, remove the tank lid and locate the fill tube. It’s small and connects the fill valve with the overflow tube. This tube pushes water down the overflow tube to refill the bowl after a flush while the tank also refills.

If the fill tube falls off, the bowl won’t fill, and the next flush will be weak. Reattach the tube and connect it to the fill valve – it should fit around two centimeters above the rim of the tube. After you’ve reattached and connected the tube, flush and watch to make sure the water goes down the tube.

open toilet tank against a blue wall
Toilet cistern in a domestic bathroom

2. Adjust the Fill Height

The water level in the toilet is adjusted via the float. If the float is too low, it will result in a weak flush. If the float is too high, the water will spill into the overflow tube and the fill valve won’t work properly, which would result in a running toilet.

Start by looking at the fill level mark inside the toilet tank and marking it on the overflow tube. That way, you will see it more easily. Measure down 1 inch and make a mark on the overflow tube. Then, flush the toilet and check if the water reaches the mark. The water should reach this mark but not go past it.

If the water doesn’t reach the mark, you will need to adjust the toilet tank float. It’s worth noting that if you have an old model, you may need to bend the rod to make adjustments. Flush the toilet after each adjustment until the water reaches the mark as expected.

You should also make sure that the water level is at least an inch below the C-L mark. If your fill valve is broken or defective, you will need to buy a new one. A nice detail is that you won’t need to buy the exact model for a replacement, as most fill valves are universal and fit most toilets.

3. Adjust the Flush Handle / Flapper Chain

If the chain in your toilet tank is too short, the flapper won’t be able to close, which will cause the toilet to leak. It will also cause the fill valve to go on and off to refill the toilet tank. If the chain is too long, however, it won’t open the flapper wide enough, which can’t prevent the flush from completing.

If your flapper chain isn’t the right length, you should adjust the linkage in the chain to have only a small slack when the flapper is closed. Cut off any excess chain and leave around an inch, just in case. Then, put the toilet tank lid back, and check if the flush rod strikes the lid when you press the lever. If it does, keep adjusting until everything lines up as expected…

adjusting a toilet check-fill-valve

4. Replace the Flapper

If you have completed all of the above and the toilet is still running, you may need to replace the flapper. Turn off the water supply to the toilet, remove the tank lid, and take out the flapper. For this equipment, you will need to bring in the old flapper to the store to buy the exact model as a replacement.

Read our guide about how to properly remove a toilet flapper.

However, the range of flapper styles has increased during the past 15 years, so you might not be able to find the same model. In that case, you should buy a model that’s most similar to yours, or buy the one with the “universal” label. As most flappers are relatively affordable, you might also consider buying both models and checking which one works best.

If you still can’t find the right flapper, you may need to replace the entire overflow tube. On most toilets, this process includes removing the tank. However, this process isn’t too difficult and will take you about an hour. If you’re comfortable with your DIY capabilities, you could replace the overflow tube on your own and save on the cost of a plumber.

The Bottom Line

Repairing a running toilet is a DIY job, which can be done by any homeowner. By working through each of the steps we mentioned, you will have your toilet fixed in no time. If using our steps listed above does not not work, then its time to consider calling a professional plumber.