It’s a common problem in many households. You have just flushed your toilet, and instead of hearing a single flush, you hear two. What just happened, after all, you only pressed the flush lever once?

The reason is that your toilet tank is releasing too much water into the bowl. As soon as your toilet finishes one flush, it is getting enough water to start the process again

My Toilet Flushes Twice

Your toilet is driven by the action of water flowing over a bend in the pipe drawn down by gravity. Then the water seals against air from below, creating suction drawing more water from your bowl.

Because this relies on the water in the bowl to fill the pipe, it stops when it runs low. This creates the gurgling sound at the end of the flush when the air begins to break up the seal. 

But when your toilet flushes a second time, it means that the bowl continued to receive water after the flush ended. Once it received enough water quickly enough, it caused the toilet to flush a second time.

Your Toilet Flapper isn’t Working Properly

Your toilet flapper is responsible for releasing the water from the tank into your bowl every time you press the flush lever. But, if it doesn’t correctly sink back down after every flush, it will continue to release water causing another flush. 

Common causes of this are flappers that are too light, hard water buildup, and inappropriately set flapper chains.

The Toilet Has Hard Water Buildup

Hard water buildup can create a layer of gunk on the bottom of your toilet. This sometimes happens between the flapper and seal or the flapper’s hinge. The buildup can stop the flapper from lowering or creating a seal. To solve this, follow these instructions.

Drain your toilet tank. Turn the shutoff valve behind the toilet clockwise until it stops. Then, flush the toilet until the tank is nearly empty.

Remove the flapper. The flapper mounts to the overflow tube generally by hinging on small protrusions. Remove the flapper from the overflow tube. 

Clean the flapper and hinges. Use a sponge and some distilled vinegar and gently wipe both the hinges of the overflow tube and the flapper down thoroughly.

Wipe the seal. Before reinstalling the flapper, gently wipe the seal where the flapper rests with the sponge and vinegar. 

Reinstall the flapper. Reinstall the flapper making sure it rests against the seal, and the hinges are correctly installed against the overflow tube.

The Flapper is to Light

If the flapper is too light, it needs to be replaced. If your flapper has been replaced with a universal model at some point, this is the most likely cause of your problem.  To test, simply flush your toilet while watching. See if the flapper comes back up after lowering or if it does not come back down for too long.

Flapper Chain Needs to be Adjusted

If your toilet chain is improperly set or getting a kink in it, this may be causing your flapper to improperly seal. This needs to be solved by modifying your chain. Follow these steps.

  1. Inspect the chain. Check the chain for areas where the chain could have bound up and squeeze these areas straight. Also, look to check if chain slack is getting caught between the flapper and seal
  2. Push down on the flapper. See if the flapper can travel all the way down. If not, this probably means the chain is set too short.
  3. Adjust the chain. Look at the bar connected to your flush lever. Typically you will slot the chain into a series of holes running down it. Avoid too little slack that may hold the flapper open, or too much risking chain jamming the flapper open.

Too Much Water in the Tank

If the water level is too high in your tank, this will drain too much water into your toilet bowl. This can cause it to flush twice. To solve this, you need to adjust your float valve.

Float Ball: To adjust these, you need to determine if you have an adjustment screw. If so, use this to lower the float, thus reducing the water refill level. If not, it may use a brass arm, in which case you would gently take and bend it to lower the float.

Float Cup: These generally have a clip you can depress to adjust the float up and down. Lower it to adjust the water level down. Some models of these have an adjustment screw as well, if this is the case just use it to lower.

Fill Valve Needs Adjusted

If the fill valve is not working correctly, it may allow too much water into the toilet bowl. This could cause the toilet to flush twice. You can adjust this valve to solve the problem.

You can adjust the fill valve by removing the screw from the fill valve and moving the float arm lower. Next, replace the screw. Then, flush the toilet to see if the solution worked.

You may need to try a few times. If it still doesn’t work. You may need to replace the fill valve.

Replacing the Fill Valve

If your toilet flushes twice, it may be necessary to replace the fill valve. To do so, follow these steps:

Removing the Fill Valve

To remove the fill valve, follow these steps.

  1. Remove the toilet tank top.
  2. Disconnect the refill tube on the fill tube from the overflow tube.
  3. Flush the toilet until the tank is drained.
  4. Use a sponge or rag to dry the toilet tank.
  5. To avoid a mess, put a bucket under the supply tube.
  6. Remove the coupling nut from the shank located on the bottom of the tank.
  7. Then, use an adjustable wrench to loosen and remove the locknut from the shank.
  8. Now, remove the fill valve.

Replacing the Fill Valve

Now that you have removed the fill valve, you need to install a new one.

  1. Turn off the water. Find the shutoff valve behind the toilet and turn it clockwise.
  2. Assemble the new fill valve. Take the rubber washer from the kit and place it on the bottom flange of the fill valve tailpiece. Also, check to ensure that your fill valve will fit your toilet. Do this by moving the screw on the stem piece until you reach the correct height.
  3. Install the Valve. Place the fill valve in and connect the nut and water supply to the bottom.
  4. Install the fill hose. Check that the rubber tube is the correct length by cutting it to fit your toilet. After this, place one end on the top of the fill valve. Then, put the adapter on the other end of the tube and attach the adapter to the top of the overflow tube.
  5. Check the repair. Turn on the water. Turn the valve counterclockwise until you feel resistance. Fill the toilet tank to the marked line in the tank, and see if the toilet flushes only once.

Wrapping Up

Hopefully, you now have clear vents, a toilet without cracks, and a home that smells fresh. However, if none of these procedures worked for you, it may be necessary to call a plumber.