How to Determine the Pit Distance of Your Installed Toilet

When installing a toilet, it’s important to determine the specifications based on the pit distance. However, if the toilet has already been installed, how can you check the pit distance?

Checking the Pit Distance of an Already Installed Toilet

Once the toilet is installed, you can measure the distance from the toilet's mounting holes to the back wall to determine the rough-in measurement.

If the toilet is installed and the tank is flush against the wall, you can measure directly from the mounting holes. Use a tape measure and extend it to the back wall; this distance will give you the rough-in measurement.

According to standard toilet specifications, there are generally two sizes: one is 300 millimeters, and the other is 400 millimeters.

How to Measure the Toilet Pit Distance

1、Measuring the pit distance of the toilet should ideally be done before installation; then you should take this data with you when purchasing a compatible toilet. For accurate measurement, you need to locate the center of the drainage pipe and measure the distance to the wall. If tiles are already on the wall, this measurement will be the most accurate.

2、If the tiles have not yet been installed, you should consider the thickness of the tiles, which is generally around 6 to 8 millimeters. If you also consider the thickness of the putty layer, the total thickness might range between 10 to 15 millimeters.

3、Toilets have two types of drainage methods. Generally, the most common choice is for floor drainage, which can be siphonic or washdown toilets, while wall drainage can only use washdown types. The pit distance for wall drainage is usually 100 millimeters, while for floor drainage, the common sizes are 300 millimeters and 400 millimeters.

What to Do If the Purchased Toilet Doesn’t Match the Pit Distance

If you have already bought the toilet, but the pit distance doesn’t match the toilet, you can make some adjustments to the wall. If the pit distance is smaller, you can remove part of the wall behind the toilet and install the toilet closer to the wall, then repair the wall tiles afterward. If the pit distance is too large, you can build an additional wall behind the cistern.

In summary：the proper procedure should be to measure the pit distance first, then purchase the toilet to prevent issues during installation. If the sizes do not match, a spacer can be used, but its movement range is limited and it may affect the flushing performance in the future.