Why Does My Toilet Randomly Run for a Few Seconds?

In today’s day and age, when we usually hire someone to do the fixing around our home, quirks of our appliances and plumbing can be a mystery. You might wonder whether an occurrence is normal, or whether it means its time to call the repair person. One such instance is when your toilet runs for several seconds unprompted. There are many reasons why this might happen, but the most common are an incorrect water level or an incorrectly assembled flush valve. Both are easy fixes and can save you money on your water bill.

How Does Water Run Through a Toilet?

Water in a toilet makes the journey through two valves. First, it is taken in through the water supply (the pipe going into the wall). Then it is drawn through the fill valve into the tank. The tank will fill until it reaches the fill line, which is decided by the fill arm. If it overfills, there is an overflow pipe, which is part of the flush valve.

The flush valve also includes the chain and flapper, which are the parts that move when you pull the handle to flush. When the handle is down, the flapper is pulled up to create an opening from the tank to the bowl which refills the bowl after flushing. Water that is flushed is sent down the u bend in the toilet, and into the septic system of your house.

Why Does My Toilet Randomly Run?

The first suspect when your toilet runs should be the flush valve. This is a valve that controls the flow of water into the toilet when you flush. If its hardware is slightly off center, loose, or ill fitting, it can cause the toilet to run excessively. The flush valve is made up of the chain, flapper, and overflow tube. You should check that the chain is neither too short nor too long, and that the flapper is sealing well without damage or warping. It may also cause problems if the flapper looks very dirty.

Alternative Reasons Your Toilet is Running Randomly:

If the usual suspects do not solve your problem, you can also check several other parts such as the overflow tube, the float arm height, and the fill valve.

The Overflow Tube

If the flush valve is the problem, and you have checked the chain and flapper, then the problem might be the size of the overflow tube. If the overflow tube is too short, then the entire flush valve will need to be replaced. Your overflow tube should be about one inch above the toilet’s fill line.

The Float Arm Danco 80816 Complete Toilet Repair Kit Fill Valve, Flapper, Rod, Float Replacement, White

Your float arm or cup is the device that tells the toilet how far to fill the tank. If the level is too high, it will drain water into the overflow tube before the fill valve closes, causing water waste.

The Fill Valve

The fill valve is the least frequent problem when encountering this issue, but on the off chance that all the above issues have been ruled out you will want to check it. The Fill Valve describes the hardware that fills the toilet’s tank from the main water supply. This valve has several rubber gaskets that might be cracked, which would cause water to continue to flow even when it is “closed.” It might also not be closing all the way due to warping. Your best solution is to replace the whole valve, which is not too expensive or difficult.

How do I Fix the Problem?

Now that you have successfully figured out which of these issues is causing your toilet to run, you can either call a professional or fix it yourself. None are particularly difficult fixes, so unless you have far more money than time, I would suggest fixing them yourself.

The Chain is the Wrong Length

  1. First, determine if it is too long or too short. It should be long enough to allow the flapper to completely close without more than a few centimeters of slack.
  2. Look closely at the chain, near the top you will notice a clasp. Simple move this clasp to a different link in the chain to adjust the chain’s length.

The Flapper is Dirty or Damaged

1. Turn off the water supply to the toilet by turning the valve that goes from the toilet into the wall clockwise. You may need a tool to do this, as it is difficult to do with your hands. An adjustable wrench is a viable choice for the job.

2. Empty the tank by flushing the toilet. You may need to hold down the handle for a couple seconds to completely drain the tank.

3. To disconnect the flapper, unhook the chain from the horizontal flush bar. The chain is usually attached via clasp.

4. Slide the side ears of the flapper off the pegs. Depending on the design of the flapper they may slide off or snap off.

5. If the flapper is dirty, then you can clean it with a vinegar and warm water solution.

6. If the flapper is damaged, you can replace it with a new one by doing the above steps in reverse.

There is a problem with the Overflow Tube one piece toilet flush valve, universal toilet repair kit complete 2 inch toilet flapper/10 inch high toilet overflow tube

1. Unfortunately, if your overflow tube is too short or damaged, then you will need to replace the entire flush valve. This is the hardest fix. First, you will want to turn off the water supply and drain the tank just as you would to replace the flapper.

2. Disconnect the flapper and remove the tank to bowl bolts.

3. Lift the tank off the bowl to access the flush valve gasket underneath. Loosen the flush valve nut – this may be easier with two people.

4. Place the new flush valve and tighten the flush valve nut. Replace the tank to bowl gasket.

5. Carefully lower the tank back onto the bowl and resecure it.

6. Reinstall the flapper and chain, then turn back on the water supply and test the new valve by flushing. Keep an eye out for leaks from the tank or bowl.

The Float Arm is at the Wrong Height

1. Your float arm should be about one inch below the overflow tube. To change the fill height, carefully bend the horizontal arm up or down.

There is a Problem with the Fill Valve

1. If you have an issue with the fill valve, you will need to replace it. Begin by turning off the toilet’s water supply and emptying the tank.

2. Use a set of channel locks to remove the water supply line

3. Remove the locking nut at the bottom of the tank and lift the fill valve out of the tank. It might be helpful to set the old valve in a sink or bucket – it will be wet.

4. Adjust the new fill valve to match the height of your toilet, then, set it in place. Use the locking nut to provide a watertight seal.

5. Reconnect the water supply and turn it back on. Make sure the tank begins to fill and stops when the fill line has been reached. If this is not the case, it may have been installed incorrectly.

What is the Best Toilet Flapper You Can Replace Your Current One With?

The toilet flapper, made of rubber and plastic, will need to be replaced every couple of years. Therefore, its one of the most common problems with your toilet. When it does need to be replaced, the sheer number of flappers on the market can boggle the mind. Which one should you choose? There are a couple of factors to consider: whether the flapper is universal, the material it is made of, and whether it is a snap on or ring design.

Universal vs. Non-Universal

Flappers can be made both for specific toilet models, and as a general model to fit most any type of toilet. Universal flappers have the obvious benefit of you not needing to know exact specifications of your toilet, however they come with the disadvantage of not being designed especially for your system. This can rarely mean it does not seal as well, or even does not fit if you have an unusual model. On the plus side, universal flappers are often cheaper since they are a generic product.


Most flappers are made of rigid plastic or rubber. Rigid plastic flappers are more durable and last longer. While rubber flappers provide the best seal and the most forgiving installation. This will really depend on your preference.

Snap or Ring Design

Most toilets attach the flapper via a set of pegs on the bottom of the tank. The flapper will snap onto these pegs, and secure the flapper, this is the snap design. Ring designs have a protruding ring that can be slid over the valve to secure the flapper and are less common. Most ring designs are also made to work with peg systems, and the ring can be cut off. Check to see which kind of toilet your have, so that you can ensure the hardware is compatible.

Writers’ Picks:

Below I have selected two highly rated universal flappers. These should fit most toilet systems and fix the most common cause of a running toilet.

1. The Korky Universal Flapper Korky 100BP Ultra High Performance Flapper Fits Most Toilets - Long Lasting Rubber - Easy to Install - Made in USA, Small, Red

This is a stiff rubber snap on style flapper. It is universal for two inch and 3-inch toilets (there is a medium and large size). It is also one of the cheaper flappers on the market. It is shaped to effectively replace ring, snap on, hard, and soft flappers. It is one of the most universal flappers available.

2. The Fluid Master Universal Flapper Fluidmaster 502P21 PerforMAX Universal Water-Saving Long Life Toilet Flapper for 2-Inch Flush Valves, Adjustable Solid Frame Design, Easy Install, Red, 1 pack

This is a stiff rubber snap on style flapper. It is universal for 2-inch toilets and rated quite easy to install. Fluid Master is one of the best plumbing replacement parts brands, so even it this flapper does not suit your needs they have a high quality one that will.

Why Does My Toilet Run After Replacing the Flapper?

If your toilet is still running after replacing the flapper, and you have set the chain to the right length, you may have installed it incorrectly or have a problem with one of the valves. Open the tank and watch each of the pieces when you flush to determine what is causing it to run.

Does a Running Toilet Increase My Water Bill?

One of the biggest reasons to fix a running toilet is that it is a waste of water. Depending on the severity of the problem, hundreds of gallons can be lost from the toilet running. Not only is this bad for the environment, but you can also expect an elevated water bill.

When to Call a Plumber?

I would not call a plumber until you have checked the chain and flapper – these are such simple fixes that it would be a shame to spend the money. However, if you are not comfortable with more labor-intensive repairs, or are not able to pinpoint the problem after going over this list then call a plumber to come out and look.