Why Does My Toilet Double Flush? (Possible Causes & Fixes)

Jessica Stone
by Jessica Stone

Imagine this: You just finished using the bathroom, press down on the handle to flush and after the first, anticipated flush, your toilet unexpectedly flushes a second time. If this scenario is happening in your bathroom, you’re not alone. In fact, this is a very common occurrence that homeowners experience. There are a number of reasons why your toilet may be double flushing. While there might be some do-it-yourself ways to troubleshoot and fix the problem, calling in a professional is always the recommended route to obtain a proper diagnosis.

The two main causes for a toilet that double flushes is a toilet flapper that stays up too long and a toilet fill valve that requires adjusting. If the toilet flapper is staying up too long, it’s likely because the flapper is too lightweight to return the proper place after the first flush. Whereas, if the fill valve isn’t adjusted to hold the correct amount of water, excess water will enter the toilet and cause it to double flush.

Whatever the reason may be, a double flushing toilet is something that should not be ignored. However, the good news is that neither of these potential causes will impact other components of the toilet. This means that once you figure out the root of the problem and fix it, you should no longer have to worry about your toilet flushing twice.

Do You Need to Install or Repair a Toilet?

Get free, zero-commitment quotes from pro contractors near you.

An Overview of How Your Toilet Works

Before we go into detail about why your toilet is double flushing and how to fix the problem, it’s important that you understand how a toilet works. Despite the fact that we use toilets multiple times throughout the day, most homeowners have no idea how they function. In fact, many of us don’t think twice about how a toilet works until it starts to malfunction.

Nowadays, most homes are outfitting with gravity-flush toilets, which are a style of toilet that has been around for over two centuries. These toilets consist of two main, basic components: the bowl and the tank. The tank stores the freshwater that is used for flushing the toilet, while the bowl holds the rest. A hole at the base of the bowl leads into the trapway, or siphon, which leads down into the floor and connects to the pipes in your home.

The flushing handle is attached to a lever in the tank that is connected to the rubber flapper via a chain. By pressing the flushing handle, the flapper lifts which allows the water stored in the tank to enter the bowl. Because of gravity, waste and water get sucked down the drain and into the sewer line. After the toilet flushes, the fill valve refills the tank the proper level and water goes through the overflow tube to fill the bowl.

All of these components must be in good working condition for your toilet to function efficiently. If any of these parts malfunction or break, it could lead to your toilet double flushing.

Why Does My Toilet Double Flush?

Put simply, your toilet is double flushing because too much water is escaping from the tank into the bowl – which forces a second flush. There are two main causes for why your toilet bowl is receiving too much water:

  • The flapper is staying up too long (lightweight)
  • The water level in the tank is too high (improperly positioned toilet fill valve)

Let’s explore these issues in further detail and the steps to get your toilet to stop double flushing.

1. Toilet Flapper Stays Up Too Long

Oftentimes, when a toilet flapper is staying up too long, this is caused by a generic or universal flapper. If your toilet is outfitted with a generic or universal flapper instead of one that was designed for your particular model, your toilet will flush twice. These generic flappers are usually too lightweight to settle back into place after a single flush. Or, they may simply not be able to provide a perfect seal. In either case, too much water is getting through and the toilet must flush a second time.

In this case, the best course of action is to simply replace the toilet flapper with one that is manufactured for your toilet. However, it’s not uncommon for toilet flappers to need replacing even if they are the proper kind.

If your toilet was ever out of use for an extended period of time with no water in the tank, the flapper may have dried out which caused the rubber to no longer provide an adequate seal. It’s also possible that the flapper simply needs to be adjusted so that it can effectively seal off the water in the tank in between flushes.

Regardless, observing your toilet flapper is the best way to know if it needs to be adjusted or replaced. To replace your toilet flapper, follow these steps:

  • Turn off the water supply to the toilet by closing the shut-off valve.
  • Flush as many times as needed to empty the tank.
  • Detach the current flapper from the flush valve by unclipping them. Don’t worry about the chain coming off, as your new flapper should come with one.
  • Pull the old flapper free from the overflow valve. If it’s made of rubber, it will pull right out. Whereas, if the flapper is plastic, it will make a popping sound.
  • Attach the new flapper to the flush valve and slide it over the tubular overflow valve.
  • Adjust the length of the chain as needed.

2. Toilet Fill Valve Needs Adjusting

Your toilet fill valve will need to be adjusted whenever the flush is too weak or too powerful. Adjusting the valve allows the proper amount of water to refill the toilet tank. When the water inside of the tank is too high, it results in too much water rushing into the pull and forcing a double flush. Whereas, when the water level is too low, there won’t be enough water to flush everything, resulting in a weak flush.

There are two ways to go about adjusting the toilet fill valve, depending on whether your toilet has a float arm or a float cup:

  • For toilet fill valves with a float arm, use a screwdriver to adjust the screw on the top of the valve and lower the arm. If you don’t see an adjustment screw, your fill valve is probably old and should be replaced with a newer model.
  • For toilet fill valves with a float cup, give the cup a squeeze and slide it down to lower the tank’s water level.

Some toilet fill valves will be outfitted with a specific water level adjustment rod that you can turn to lower the water level as needed. In some instances, it’s possible that your toilet fill valve is simply too old and needs to be replaced. Toilet fill valves have a life expectancy of only about four to five years. If yours is reaching that point, it may be time for a replacement.

Do You Need to Install or Repair a Toilet?

Get free, zero-commitment quotes from pro contractors near you.

Final Thoughts

While toilet flush issues may not seem as daunting as a hot water heater that is making a high-pitched popping sound, they are still a serious problem. Toilets are used frequently in homes and when your toilet is having flushing problems, it is an annoyance at best, but may become an urgent issue if not fixed quickly.

The toilet flapper and fill valve are just two parts that can cause flushing problems. Other possible causes may be hard water buildup in the pipe’s and pathways, which reduces the amount of water that can be supplied to a flush, or clogged pipes and drains as a result of feminine products or wipes stuck in your plumbing.

Another common flushing issue, aside from double flushes, is when a toilet doesn’t stop running. In many cases, the culprit is also the flapper but if replacing it doesn’t fix the problem, replacing your entire flush valve assembly is usually your best bet.

Jessica Stone
Jessica Stone

Jessica considers herself a home improvement and design enthusiast. She grew up surrounded by constant home improvement projects and owes most of what she knows to helping her dad renovate her childhood home. Being a Los Angeles resident, Jessica spends a lot of her time looking for her next DIY project and sharing her love for home design.

More by Jessica Stone