Why Your Toilet Flushes Twice & How to Fix It

As someone who has spent years doing maintenance at a major hotel with over 250 toilets on property and serviced thousands of issues over the last 10 years, I’ve come across my share of double-flushers. So, I understand how perplexing this issue can be.

It’s common to wonder why a toilet would flush twice instead of just once.

In this article, we’ll explore the possible reasons behind this phenomenon and provide you with solutions to fix the problem. So, let’s dive in and demystify the double-flushing toilet.

Incorrect Flapper or Flapper Chain

A common cause of a toilet flushing twice is an incorrect flapper or a flapper chain that’s improperly adjusted. The flapper is the rubber component that sits at the bottom of the toilet tank and is responsible for releasing water into the bowl when the toilet is flushed.

If the flapper doesn’t close properly or the chain is too short, the flapper may reopen after the initial flush, causing a second flush.

How to fix: To remedy this issue, check the flapper and make sure it’s the correct size and type for your toilet. If it’s damaged, replace it with a new one. Additionally, adjust the flapper chain length so that it allows the flapper to close properly after each flush.

Pro Tip: Ideally, the chain should be set so that the flapper goes vertical when you flush, and it stays in that vertical position for about 3-5 seconds before dropping back down.

image showing where to find flapper and chain to make repairs to a double flushing toilet.

Faulty Fill Valve

Another possible reason for a double-flushing toilet is a faulty fill valve. The fill valve is responsible for refilling the toilet tank with water after each flush. If the fill valve is damaged or improperly adjusted, it may not shut off the water flow in time, causing the toilet to flush twice.

How to fix: Inspect the fill valve and check for any signs of damage. If it’s damaged, replace it with a new one. If the fill valve appears to be in good condition, adjust the water level in the tank according to the manufacturer’s instructions.

Pro Tip: Before replacing your fill valve assembly, it’s best to try cleaning it beforehand, as mineral deposits such as calcium in the water can build up inside the valve and cause it to malfunction. To clean a fill valve, you can follow my instructions in this article with pictures to guide you along.

image showing where to find the fill valve to clean or replace if a toilet is flushing twice.

Insufficient Water in the Toilet Tank

If the water level in the toilet tank is too low, it may cause the toilet to flush twice. When there’s not enough water in the tank, the flapper may close too quickly, causing a weak flush. The toilet then flushes again to compensate for the insufficient water used in the initial flush.

How to fix: Adjust the water level in the toilet tank to the appropriate level, typically marked on the inside of the tank or in the owner’s manual. This should ensure that there’s enough water for a complete flush each time. If your toilet tank won’t seem to hold water as it should, then check out this article on why that’s happening and what you can do to remedy it.

Pro Tip: Generally, having the water fill to about 1″ below the top of the overflow tube is the correct height for the water in your tank.

image showing the correct water height in the tank to rule out one reason for a toilet double flushing. — The water in this toilet is about 1″ below the top of the overflow tube.

Low Water Pressure

Low water pressure can also cause a toilet to flush twice. If the water pressure in your home is too low, the toilet tank may not fill up quickly enough, causing the flapper to close prematurely and resulting in a second flush.

How to fix: Check the water pressure in your home and adjust it as necessary. If you’re unsure how to do this or if the problem persists, consult a professional plumber for assistance.

Pro Tip: Check to make sure your toilet’s water supply valve is open all the way by turning the valve counterclockwise.

Make sure the valve is completely open for proper water pressure to the toilet (counter clockwise).

Partially Clogged Trapway or Vent Pipe

A partially clogged trapway or vent pipe can also lead to a double-flushing toilet. The trapway is the curved section (looks like a goose neck) of the toilet bowl that connects the bowl to the drainpipe. The vent pipe helps regulate air pressure in the plumbing system. If either of these components is partially clogged, it can cause the toilet to flush twice.

How to fix: Use a toilet plunger, toilet auger, or snake to clear any blockages in the trapway. If the problem persists, it may be a clogged vent pipe, which should be inspected and cleared by a professional plumber.

vent pipe on the roof that is partially or fully clogged can cause pressure issues in the line and cause double flushing.

Important Takeaways

A double-flushing toilet can be caused by various factors, such as an incorrect flapper or flapper chain, a faulty fill valve, insufficient water in the toilet tank, low water pressure, or a partially clogged trapway or vent pipe.

By identifying the root cause of the issue and applying the appropriate solution, you can put an end to the annoyance of a double-flushing toilet.

If you’re interested in comparing and contrasting the various types of toilets and their water efficiency when flushing, check out my article here to see what new toilet might be best for you!

Remember, it’s important to address these issues promptly to ensure that your toilet operates efficiently and to prevent potential damage to your plumbing system. By following the tips and solutions provided in this article, you’ll be well-equipped to tackle the problem and restore your toilet’s functionality.

So, the next time your toilet decides to flush twice, you’ll know exactly what to do to fix it!