Why Does My Toilet Flush Twice?

September 28, 2017

Your toilet is flushing twice because too much water is escaping from the toilet tank into the bowl, forcing a second flush.

So why is your bowl getting too much water? Well, you can trace that problem back to 1 of these 2 issues:

  1. A lightweight flapper
  2. Water level in tank is too high

We’ll explain how to troubleshoot these 2 issues later in the article. But first, let’s go into a quick refresher on how a toilet works...

How your toilet works

Toilets are fairly simple mechanisms with 2 main parts: a bowl and a tank.

When you push down the handle, water that’s stored in the tank runs into the bowl. And, because of gravity, once enough water pours into the bowl, the waste and water gets sucked down the drain and into your home’s main sewer line.

Clogged Drain Diagram

Once you flush, toilet water drains into the main sewer line

After you flush the toilet, the fill valve in your toilet starts to refill the tank to the appropriate level and water travels through the overflow tube to refill the bowl. Then your toilet is ready for the next flush.

Toilet Tank Parts Labeled Diagram

Toilet parts found in tank

Here’s how the flush process works in more detail, step by step:

  1. When you push the handle, it pulls on a metal chain connected to a flapper.
  2. The flapper lifts and releases the tank water down the flush valve (located right under the flapper) into the bowl.
  3. Because of gravity, tank water pushes the water from the bowl into the trap, which then exits through the main drain.
  4. Once the tank is empty, the flapper closes, preventing water from entering into the bowl.
  5. The fill valve is activated, which brings in water from the supply line into the tank. Some of this water enters the fill (overflow) tube, which refills the water in the bowl.
  6. Once the tank reaches the set water level (measured by the fill valve or the floating ball, depending your toilet), the supply water shuts off. 
  7. Then, your toilet is ready to flush all over again!

If you’re a visual learner, this video shows these steps in action.

Now let’s look at the issues that might cause your toilet to flush twice...

Double flush problem #1: Lightweight toilet flappers

The toilet flapper is a little rubber “trap door” that opens to let the water stored in the tank pour into the toilet bowl.

But if the flapper doesn’t weigh much, or it’s not adjusted properly (more on that below), it won’t close fast enough after you press the handle to flush the toilet. This means more water from the tank continues to enter the bowl even after the first flush is complete. And, because a toilet flushes due to gravity, once enough water enters the bowl again, the toilet will flush a second time.

How to fix it:

  1. Take the lid off the toilet tank and flush the toilet. Look at the flapper. Does it close on its own? Or does it stay open a while? If it stays open, you know the flapper is what’s causing the double flush.
  2. If you have an adjustable cone-style flapper, try turning the dial on top of the flapper. This will open up larger holes in the top of the flapper, which releases air caught inside of the flapper, making it less buoyant. As it loses air, the flapper is forced to sink quickly, sealing off water (and avoiding that annoying second flush). 
  3. If your flapper isn’t adjustable, it means you’ll need to replace it with a heavier model. Don’t worry—this isn’t very difficult and we’ll walk you through steps on how to do it. 
    1. First, go to any home improvement store and go to the toilet/plumbing section. You’ll usually find a variety of flapper options, but look for one that matches your toilet’s brand/model or says “universal size.” Also, the heavier the flapper, the better.
    2. When you get home, turn off the water supply to your toilet. The water supply valve is usually located behind the toilet.
    3. Then, flush your toilet to drain any excess water.
    4. Remove the old flapper (most snap over little ears on the overflow tube).
    5. Install the new flapper by attaching it to the overflow tube. Make sure you reconnect the chain to the flapper, and that there’s just the right amount of slack (not too tight, not too loose).
    6. Open the water supply and test it to make sure it works.

Need help installing a new toilet flapper? Give us a call, we’d be happy to help. 

Flapper not the issue? Your tank may have too much water in it...

Double flush problem #2: Too much water in your tank

Too much water in your tank means that when you flush your toilet, that extra water will continue to pour into the bowl, refilling it quickly and causing your toilet to flush twice.

Toilet Fill Valve

Toilet fill valve

So, why is there too much water in your tank? Well, it’s usually because the toilet fill valve is set improperly. (Remember: the toilet fill valve is the component that controls how much water stays in your tank.) Luckily, most toilet fill valves can be easily adjusted to limit the amount of water in your tank.

How to fix it:

  1. If your toilet fill valve has a float arm, take a screwdriver and adjust the screw on top of the fill valve to lower the float arm. Don’t see an adjustment screw? Your fill valve is probably too old, so it should be replaced with a newer model. Contact a plumber to install a new fill valve float arm.
  2. If your toilet fill valve has a float cup, squeeze the float clip and slide it down to lower the water level in the toilet tank. Some models have a water level adjustment rod, which you can turn to lower your toilet tank’s water level.

Need help adjusting the water in your tank? We’ve got you covered, just give us a call.

Need a plumber to fix your toilet’s double flush?

Contact Red Cap Plumbing. We’ll send over one of our skilled plumbers to get your toilet flushing properly again. 

  • Posted in:

Similar Articles: