How to Detect Toilet Leaks

Last Updated: March 26, 2023 References

Toilet leaks may be easy to repair, but detecting them can be a great challenge, especially when they are completely silent. It's nerve racking to view a water bill and see the amount double or triple what you normally pay for. Here is a very quick and easy method to detect a toilet leak.

Method 1

Method 1 of 2:

Using Food Coloring

1
Remove the tank lid of the toilet.^{[1]
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2
Flush your toilet as usual. Wait for the water to rise again to the designated water line of the tank and the toilet to fully complete a flush.

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3
Drop about 4 to 5 food coloring drops in the toilet tank. You may want to use a dark color such as blue or red instead of yellow.^{[2]
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4
Replace the toilet lid and wait 20 to 30 minutes.
5
Survey the toilet bowl. If the water is clear, there is no leak. If the water has changed color, there is a leak present.^{[3]
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6
Repeat the process with all toilets in the house, if applicable. This is very important to see if the issue is coming from one specific toilet or happening in multiple ones.

Method 2

Method 2 of 2:

Looking for Other Signs

1
Look at the water level. First, remove the toilet tank lid. If the water level is well above the overflow pipe, check the float. The float rises with the water and tells the inlet valve on the ballcock (the float) when to shut off the water valve. If the water keeps flowing past the overflow tube, there is likely a leak.
- To check the inlet valve, flush the toilet and lift the rod that holds the float as the water rises. If you hear the water stop, the problem is caused by the float, and it likely needs to be replaced. A new float and rod are very easy to replace and will only cost a few dollars at the hardware store.
2
Test the flapper. If the water level of the tank is not surpassing the overflow tube, but you still hear or see excess water flowing into the bowl, it’s time to check the flapper. The flapper is a round rubber seal that sits at the bottom of the tank. Its purpose is to stop the water inside the tank from entering the toilet bowl.^{[4]
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- Turn off the water supply valve near the toilet, and check if the water level in the tank decreases. If there is a decrease after 15-20 minutes, the problem could be due to the flapper. There could either be a leak in the flapper, or the chain may be too tight.

Community Q&A

Question

If a toilet slips off the wax seal, will it leak?

Community Answer

Yes, it will leak because the wax ring is what holds the pressure on the toilet. It helps the toilet flush, so if the wax seal is bad, the toilet will seep water out into the sewer. You can tell if the seal is bad by using a wax pencil to mark your water line at night when you go to bed. In the morning, if the water is below the mark, you need to replace your wax seal.
Question

After I flush the toilet, it makes a hissing noise that's coming from the tank. What could be the problem?

Douglas E. Roberts, Author

Community Answer

The fill valve is not shutting off when the tank gets full of water. Look in the tank to see if water is coming up over the overflow tube. The water level should be just a little lower than that.
Question

What will fix this problem?

Community Answer

Replacing the "flapper" will usually work. Replacements can be found at Home Depot, Lowe's, Walmart, etc.