Why does the toilet keep running

3 Simple Reasons Why the Toilet Keeps Running and How to Fix It

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Kevin Jefferson

October 20, 2021

A running toilet is a problem you’ll want to address sooner rather than later. It can rack up your water bill by wasting hundreds of gallons of water a day and has the danger of overflowing the toilet bowl.

But don’t call the plumber just yet; there are a few things you can try on your own to deal with a running toilet. Here are the three most common causes of a constantly running toilet and a few ways you can fix them.

The Toilet Flapper is Not Working

toilet flapper value

Inside your toilet tank, there is a small rubber valve called a toilet flapper. Th toilet flapper prevents the water from draining by sealing the flush tube.

When you flush the toilet, the lever lifts the flush valve, allowing the water to drain. A worn-out toilet flapper or flush valve is the number one cause of a running toilet.

Shut off the water to the running toilet so you can check the toilet flapper for problems. The shutoff valve is behind the toilet tank and connects to the water line.

Many older toilets do not have water supply lines with shut off valves. If that’s the case with yours, try turning off the main water supply to your home. After you shut off the water, flush the toilet.

Remove the Toilet Tank Lid

But, before you do so, grab a towel and lay it somewhere away from the toilet bowl where it won’t get in the way. Place toilet lids that are made of ceramic on the towel to prevent yours from getting scratched. See this post on toilet tank parts for more help.

Adjust the Toilet Chain Length on the Running Toilet

If the chain that pulls the flapper is too short or too long, it can also cause problems. It will pull up the flapper if it’s too short, or it can get underneath the flapper if it’s too long.

Whatever the problem is with your toilet bowl, the fix is simple. First, if the flapper chain is too short, remove its hook from the lever. Then, to give the chain more slack, move the hook up two links or more if needed, but not too many as there should be enough tension for everything to work correctly. Then, reattach the hook to the lever.

If the chain is so loose that it keeps getting caught under the flapper, remove the hook, and then remove a few links from the top of the chain using a wire cutter. Attach the hook back onto the chain and hook it to the lever.

Check the Flapper for Damage

If the toilet keeps running, you need to remove the flapper so you can properly inspect it. First, pull the edges of the rubber valve from the mount pegs located on the overflow tube.

Clean the Flapper

If the flapper has mineral buildup on it, the mineral deposits may be preventing it from sealing correctly. So first, clean it off and then put it back in place; this might be the solution.

Replace the Flapper

If you have a toilet that keeps running, and the flapper appears worn out or damaged, it’s time to get a new toilet flapper. There are various types of rubber valves, so it’s best to purchase a universal flapper. You don’t need to waste time trying to find the perfect replacement.

But, you will need to make sure you get the right size of flapper for your toilet bowl. For example, if the rubber valve in your toilet tank is the size of a grapefruit or a softball, you need a 3″ flapper. If it’s the size of an orange or baseball, you need a 2″ flapper. Toilet flappers can also cause problems with the toilet tank not filling correctly.

Once you get a new flapper, mount it on the pegs and hook the chain to it. To check whether this has solved the problem, turn the water back on and flush the toilet. If the toilet still keeps running, the water level in the tank may be the problem.

The Water Level is Too High

In every toilet tank, there is a tube that prevents the water from overflowing. The water will continuously drain down that tube when the water level is too high.

Adjust the Toilet Float

Toilet Float and overflow drain

In the middle of the tank, you’ll find an open tube. First, examine the overflow pipe with the tank full while the water is still running. If the water continuously runs from the tank into the toilet overflow tube, you need to lower the float.

The toilet float is a device that lowers or rises with the water level. It’s attached to the fill valve. When the float reaches a certain height (when there’s enough water in the tank), it “tells” the valve to shut off the water. So, you can adjust the water level by adjusting the float valve.

Determine the Type of Float in Your Toilet Tank

There are two main types of floats. Your float is either a float cup fill valve or float ball fill valve, the image above has a blue float cup.

Float cup valve: If there’s a tiny plastic cylinder wrapped around the valve, it’s a float cup valve. This type of float works by sliding up and down the valve shaft.

On top of the toilet valve, you’ll find a screw. You can adjust the height of the float by turning this screw counterclockwise. A quarter turn should do it. To check whether it has worked, flush and refill the toilet tank.

The water level should be 1″ to 1.5″ below the opening of the overflow tube. If necessary, turn the screw a bit more.

Float ball fill valve: If you find a rubber ball floating in the tank, that’s a float ball valve. It should have a long float arm that connects it to the valve. If there’s water inside the float ball, you will need to replace it. A universal float ball should be easy to find.

Float ball fill valves are adjusted much in the same way as float cup fill valves. At the point where the float arm is attached to the valve, you’ll find an adjustment screw. To lower the float arm, turn the screw counterclockwise.

Flush the running toilet and wait for the tank to fill. If necessary, continue adjusting the screw. If you can’t get the water level to be 1″ to 1.5″ below the opening of the overflow tube, the valve is most likely not working correctly.

The Fill Valve is Broken

fill valve

Generally, it’s a good idea to replace this valve about every five years as it wears out over time. After that, you can install a universal valve, but the top of the valve should be 3” above the top of the overflow tube, so it needs to be the right size.

Most universal valves allow you to adjust the height, but if you don’t want to take any chances, you can bring your old valve to the hardware store to find the perfect replacement.

Disconnect the Toilet Water Supply Line

Plumber shuts off water supply line

Like in step one, you need to shut off the water to the running toilet completely. Then, flush the tank and make sure it’s empty.

Before you disconnect the water hose, place a plastic container underneath it. You’d want to avoid making a mess if there’s some water left in the hose.

Grab a pair of pliers and unscrew the lock nut that secures the water hose to the underside of the toilet tank. Now you can safely disconnect the water supply line.

Remove the Fill Valve

On the underside of the tank, there’s another lock nut that holds this valve in place. Use an adjustable wrench to remove it. Then, you can remove the valve.

Install the New Fill Valve

The new valve should come with a shank washer, a cone washer, and a refill tube. With the beveled edge of the shank washer facing down, put the shank washer onto the bottom of the valve.

Then you can place the valve inside the tank. Next, place the cone washer onto the part of the valve that is sticking out outside the tank, where it connects to the water pipe. Each washer must create a water-tight seal around its connection point.

Now, you can tighten the lock nut. It’s best to do it by hand as you don’t want to tighten it too hard. You can easily crack the toilet tank if you tighten the lock nut with a wrench.

Attach the Refill Tube

Attach the new refill tube to the nozzle located at the top of the valve. Then, clip the other end of the refill tube to the overflow tube.

While ensuring the washer is firmly in its place, connect the water hose to the valve. Then, turn the toilet water back on and wait until the tank fills.

Adjust the Float

Check the instructions to see what’s the correct float height for your new valve. Then, turn the adjustment screw to adjust the float. When adjusting the height of the float, you can use a tape measure to make it easier.

Flush the Toilet

Person flushes a toilet

It’s time for the final test. Flush the toilet to see whether it still keeps running. If there are no leaks and the water is no longer running, congrats, you are done! If none of this has worked and the toilet still keeps running, then it is time to call the plumber.

A running toilet is a real nuisance that is one of the reasons I wrote about the best flushing toilets. But the fix for a running toilet is simple, it takes no longer than 15 minutes, and anyone can do it.

For more help, read this post on different types of toilet flush systems.

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