Depending on the extent of the leak, a warped or poorly fitting flapper can waste up to 200 gallons of water a day and may cost hundreds of dollars a year.
What's a flapper?
A flapper is a rubber mechanism in your toilet tank that is the moving part of the flush valve, sealing water into the tank and allowing water to exit the tank when you flush.
Flappers deteriorate over time as a result of in-tank cleaning products and chemicals used by utilities. That's why they need to be checked every year to make sure they're fitting tightly over the flush tube. Otherwise, you end up with a leak that wastes a lot of water and can seriously increase your water bill.
Is your toilet running?
Getting to the bottom of a leaky toilet can be perplexing. To find out where your leak is coming from, some detective work is probably in order.
To find out if a leak is being caused by the flapper, put a few drops to one teaspoon of food coloring or a dye tablet into your toilet tank. Wait about 15 minutes. If you end up with color in the toilet bowl, you probably have a leaky flapper that needs to be replaced.
How much water does a bad flapper waste?
Depending on the extent of the leak, a warped or poorly fitting flapper can waste up to 200 gallons of water a day and may cost you hundreds of dollars a year.
Source: toiletflapper.org