What Size Flapper Do I Need?
You discovered there are some differences in flush valve systems and that toilet sizes can vary. Although different types of flappers exist, size is the most important factor when choosing the right universal replacement. An easy reference is to look at the size of the flush valve drain opening at the bottom of the tank.
If it’s about the size of an orange or baseball, you need a standard 2-inch seal. If it looks more like the size of a grapefruit or softball, you need a large 3-inch seal. You can also measure the flush valve opening to determine what toilet flapper size you need.
How to Measure Your Flapper
Toilets and their flush valve systems come in different sizes and shapes. Flappers are available in two sizes: standard two-inch and large three-inch. Most toilets use the standard two-inch flapper, but large three-inch flappers have become popular since the year 2000.
To quickly determine your toilet's flapper size, shut off the water supply and measure the flush valve opening to determine if you need a standard two-inch or a large three-inch flapper.
If you don't have a ruler or tape measure, look at your old flapper. If it is about the size of a baseball or an orange, you need a two-inch flapper. You need a three-inch flapper if it's more like a softball or grapefruit.
