The Easiest Ways to Fix a Running Toilet

Ah, the toilet. An invention so perfect we haven’t made any substantial updates to it in the five centuries or so since its introduction. The flush toilet you’re using today is essentially the same design introduced by Sir John Harrington in the 16th century — it relies on a water supply and gravity, and uses a surprisingly simple mechanism to make your waste magically disappear into your septic or sewer system. Like anything else, though, it can turn against us.

On one end of the disaster scale, it can clog and overflow, turning an average day into a waking nightmare. On the other end of that scale, it can start running constantly. Your toilet endlessly filling up with water might seem like a minor problem, but a constantly running toilet is costing you money — that water being pumped into your home ain’t free.

Luckily, fixing a running toilet is actually pretty simple and usually doesn’t require calling a plumber — here are some easy ways to stop a running toilet yourself.

How a toilet works

First, let’s take a crash course on how a toilet works. Look at the wall behind the toilet — you should see a valve with a hose running to the toilet tank. That’s your water supply. You can turn off the water to the toilet if you think you’ll need to replace something, but while you’re in diagnostic mode, it’s best to leave the water running because you might need to refill the tank a few times.

There are a lot of different toilet designs out there, but the basic ingredients of a functioning toilet are the same: Fill valve and tube, float, and flapper. The fill valve lets water into the tank until the float hits a certain level and then shuts off, and the flapper lifts when you use the handle or button on your toilet, releasing that water into the bowl for the flush and starting the whole process over again.

Now that we have a basic idea of what we’re looking at, there are four common reasons your toilet won’t stop running, and each of them is pretty easy to fix.

Check the flapper and chain

Probably the most common reason a toilet runs and runs is the flapper. That’s a rubber or plastic piece that fits over the flush valve, stopping water from flowing into the bowl. If the flapper doesn’t fit over the valve properly, small amounts of water will leak into the bowl on a constant basis, causing the tank to enter an infinite refilling loop. If the classic “jiggle the handle” technique actually works for you sometimes, this is probably your problem because that jiggle essentially re-sits the flapper.

Take a stick of some sort and press down gently on the flapper. Does the toilet suddenly stop running? Then you have your culprit. There are two ways to fix this:

• Replace the flapper. Examine the flapper itself. Is it warped and discolored? If it has warped, it will never fit the flush valve properly again, so you have to replace it. They’re cheap, and you can purchase universal flappers that will work in just about any toilet.
• Fix the chain length. The flapper is lifted by a chain when you use the handle on your toilet, then slowly settles back into place as the tank fills up. If the chain is too short, it can prevent the flapper from going all the way down to create a seal over the flush valve. If it’s too long, it can become caught under the lip of the flapper with the same result. Cutting a long chain back with some pliers or replacing the chain with a slightly longer one will often solve your problem.

Check the float

If the flapper looks like it’s in good shape and isn’t your problem, check your float next. The float is a large plastic cylinder or sphere that literally floats on the water in the tank. As the water goes down, the float goes with it, opening the fill valve so more water can rush into the tank. Once it floats back to its original position, the valve is closed and the water stops.

If the float is set too high, the tank overfills and water spills into the overflow tube (which is there to prevent your tank from overflowing). Because water keeps getting spilled into the overflow tube, the float never gets high enough to cut off the inflow, and the dreaded cycle of endlessly running water begins.

The float is adjustable — there’s usually a simple screw you can turn that will change the height of the float. Look at the inside of your tank — there’s probably a mark etched in there showing the fill level, which is where you want your water level to be after the fill cycle. Then look at the fill valve in the tank — there will be a “critical level” marked on it. The water level should be about an inch below this mark no matter what’s etched in the tank (because different toilet kits are installed in different ways). Adjust your float until the water level refills to that point, and see if that solves your problem.

Check the fill tube

Finally, look at the fill valve, which is the tube running up from the water supply connection, connected to the float. There will be a short plastic tube extending from the fill valve to just above the overflow tube. When you flush your toilet, water flows through this tube into the overflow, refilling the bowl. If it isn’t positioned properly, not enough water will get into the bowl, which can result in a constantly running toilet.

If it’s fallen off completely, reattach it and make sure it’s on firmly. Also make sure the end of the tube is positioned above (or sometimes, directly into) the overflow tube. Flush the toilet and make sure all the water from the fill tube is going into the overflow tube. That should solve any problems stemming from this piece of wondrous toilet technology.

If none of these fixes work, the next step is to replace the inner workings of your toilet (if you’re not sure about what’s in there, you can buy universal repair kits) or call a plumber.