How to Fix a Running Toilet with Ease

​​​​​​What’s the solution when the toilet keeps running? Discover what causes a running toilet and what you can do to stop it.

By Ande Waggener


No matter how much care you put into your decision when you choose a toilet, at some point, that toilet is going to have problems. One of the most common toilet problems is a running toilet. So what’s the solution when the toilet keeps running?


In a traditional two-piece toilet, water should run through the tank only when the toilet is being flushed. The rest of the time, the water in the tank should just sit there, waiting to be used in a flush. Over time, though, parts inside the tank can wear, causing water to flow constantly through the system instead of just when it’s supposed to. This is what creates that sound we hear when we say, “the toilet keeps running” or “my toilet tank keeps running.” Neither the toilet nor the tank are actually “running.” Instead, it’s the water that’s running -- running through the tank even when a flush isn’t in progress.


So now that we’re clear on our terminology, let’s get down to it and find out how to fix a running toilet.


Toilet Function Overview

In tank toilets, when you flush the toilet, the lever you push opens a toilet flapper, which allows water to flow out of the tank and into the toilet bowl so it can flush. After the flush, water starts refilling the tank. The rising water lifts a float, which stops the flow of water when the water reaches a set level inside the tank. When these various parts of the flushing system are a little off, water will continue to run though the tank. That flow of water not only sounds annoying, it’s creating the exact opposite of a preferred water-saving bathroom. So it’s time to fix it.


Note: the fixes below will handle most running toilet problems in tank toilets; but they don’t apply to pressure-assist toilets.


Fix #1: Adjust the Float Height

The float inside your tank must be set to a height that creates the perfect flush. If it’s set too low, the flush will be weak. If it’s too high, you end up with a running toilet. The toilet runs because water is constantly spilling into the overflow tube so the fill valve won’t shut off. Here’s what you do to check this and fix it if necessary:


  • Remove the tank lid.


  • Note the normal water level line on the toilet tank itself.


  • Put a mark on the overflow tub (that vertical tube that comes up from the bottom of the tank) that matches the normal water level.




  • Now flush the toilet. Note whether the water stops filling the tank when it reaches the mark you made. If it does, the fill height isn’t your problem. You can move on to other potential fixes.


  • If it doesn’t stop at the proper height, you need to adjust the height. If you have an old toilet, you adjust the float height by slightly bending the rod that’s attached to the float ball you see resting on top of the water. In newer toilets, the fill valve will have either an adjusting screw or an adjusting clip. Either turn the screw or slide the clip up or down the rod to adjust the water level. You want to be sure that the water level in the tank is at least an inch under what’s called the C-L, which stands for “critical level.” This level will be marked on the valve.




Fix #2: Adjust the Flapper Chain

The handle you use to flush the toilet is connected to an arm, which is then connected, by a chain, to the toilet flapper (that rubber piece that opens and closes to let water leave the tank and run into the toilet bowl.) If the chain gets tangles or it’s too short, the flapper won’t be able to properly close. This causes water to continually leak into the bowl, which makes the toilet run. Here’s how to check the chain and adjust it if necessary.


  • Remove the tank lid.


  • Look at the chain. If it’s tangled, untangle it.


  • If the chain isn’t tangled, look at the toilet flapper. Is it raised at all, even a little? If it’s or if you can’t tell and the chain appears to be pretty taut, proceed to the next step.


  • The chain shouldn’t be loose (a loose chain can cause problems too), but it should have a bit of slack. So if your chain is too short or taut, unhook the chain at the rod then reattach it to a chain link that’s one or more links up from where it had been hooked.


  • If you have a lot of excess chain dangling, cut off any excess over an inch.


  • Replace the tank lid and flush the toilet to be sure the flush rod isn’t going to hit the lid. If it does hit the lid, remove the tank lid again, adjust the chain again so the flapper can properly function and the flush rod doesn’t lift too far.




Fix #3: Replace the Flapper

If your toilet is still running after trying Fix #1 and Fix #2, it’s time to replace the toilet flapper. Don’t worry. This is an easy thing to do, and it doesn’t cost much.


  • Turn off the water to the toilet using the turn-off handle under the toilet, at the wall.




  • Most flappers connect to projections on the base of the overflow tube, but some have a ring that slides down over the tube. So remove the flapper by unsnapping or disconnecting it from the base of the overflow tube or by removing the ring from the overflow tube.




  • Take the old flapper with you to the store to find a replacement that’s as close to what you have as possible. If you can’t find something similar, purchase a “universal” flapper. If you’re not sure, get two different kinds of flappers. They’re inexpensive. And besides, it’s a great idea to have an extra flapper on hand. Just tuck it away in whatever bathroom storage you have, and you’ll be ready the next time the flapper wears out.


  • Install the new flapper, following the directions on the package. Most new flappers have two rubber arms with holes that slip over nipple-like projections at the base of the overflow tube.




  • Turn the water back on and flush the toilet. If the toilet doesn’t run, you’ve fixed the problem. If it does, you may need to replace the whole overflow tube along with the flapper. This requires that you remove the tank from the toilet. It’s a one hour or so job, but it can be done by a DIYer following the directions on the overflow tube and flapper assembly packaging. Before you do this, however, try Fix #4.


Fix #4 Replace the Fill Valve

If you’ve tried all of the above fixes, and the toilet keeps running, this probably means that the fill valve isn’t shutting off properly and won’t no matter what you do. If this is the case, the valve itself is defective. It’s time to replace the fill valve.


  • Buy a replacement valve at the hardware or home store. (They cost between $10 and $20.)


  • Don’t worry about matching the one you have perfectly … just be sure the one you’re buying is intended to for use in the toilet you have.


  • Turn off the water under the tank.


  • Follow the instructions on the fill valve packaging to replace the valve. It usually doesn’t take more than 15 to 20 minutes to do this job.




Over 90 percent of the time, one of the above fixes will stop a running toilet. So you’re now armed with the knowledge you need to stop most running toilets in their tracks.


Images used with permission, courtesy of Ande Waggener

Next: Everything There is to Know About Composting Toilets