01 of 05
Start by Removing the Tank Lid
The annoying sound of a running toilet can be maddening, but the sound is fairly easy to understand: this sound occurs when the water supply valve (usually known as a ballcock) does not shut off at then end of the flush cycle. What you are hearing is the water continuing to pour through the flush valve at the bottom of the tank and down into the toilet bowl.
It is more than just an annoyance because a constantly running toilet can waste hundreds of gallons of water if left unattended.
This... symptom has three possible causes:
- The water supply valve is misadjusted so it doesn't sense water level in the tank properly. A simple adjustment can often fix this problem.
- The water supply valve itself is faulty and is failing to shut off at the end of the flush cycle. A complete replacement of the valve--or in some cases the seals within the valve--is the course of action.
- The flush valve (flapper) at the bottom of the toilet tank is failing to seal properly, thereby allowing water to continue to flow down into the tank. Since the water level can never reach the level required for the water supply valve to shut off automatically, the toilet continues to run endlessly.
Before you run to the hardware store to buy parts follow the following steps to find which of these problems is actually causing the symptom.
Begin by taking the lid off the toilet tank.Continue to 2 of 5 below.
02 of 05
Step 1: Check the Overflow Valve
The overflow tube is the round vertical cylinder in the center of the tank. As you watch, if you see water continuing to flow down over the lip of the tube, it's possible that the ballcock (water supply valve) simply needs to be readjusted so it shuts off when the water level is at a lower level. The method for adjusting a water supply valve varies quite a bit, so you'll need to study your particular valve to figure out how it is done.
But it's rather unusual for a water supply valve to... suddenly be misadjusted if it's been working properly until recently. It's much more likely that the supply valve is simply worn out and needs to be replaced.
Continue to 3 of 5 below.
- For step by step instructions look at Replacing A Toilet Fill Valve.
03 of 05
Step 2: Check the Flapper Chain
If the overflow is not the problem, you’ll want to check the flapper chain next. This is the chain that connects the toilet's flush lever with the flapper flush valve at the bottom of the tank.
If this chain is too short, it may not be allowing the flapper to drop down fully into the opening of the flush valve at the end of the flush cycle. This will allow water to continue flowing down into the tank, which in turn means the water supply valve will continue to run on delivering more water into... the tank.
On the other hand, if the chain is too long, it may bunch up under the flapper, preventing it from sealing after the flush cycle.
On either case, the fix is simply to adjust the length of the chain so it is neither too long nor too short.Continue to 4 of 5 below.
04 of 05
Step 3: Inspect the Flapper Seal
The third possibility is the flapper itself. As the flapper gets old it, can get so hard or warped that it can no longer provide a good seal. Even a slight imperfection could be causing the toilet to run. A few drops of food coloring can let you know if this is the problem.
Add the food coloring to the toilet tank and give it a few minutes.
Continue to 5 of 5 below.
05 of 05
Any coloring in the toilet bowl will let you know that the flapper is not sealing and needs to be replaced. Replacing the flapper (flush valve) is not a difficult job; just by a replacement that looks like the old one.
If you find yourself doing one of these repairs in your toilet and it's clear the parts are older, you might consider using this opportunity to "remodel" the inside of your toilet by installing all new parts. Sooner or later, all the internal parts of a toilet will... wear out, and when you find yourself needing to replace one, it's a good bet that others will soon need replacing, too. You can save yourself future work by proactively replacing all toilet parts at the same time. Inexpensive kits are available that offer both the flapper valve and water supply valve together.