How to Determine a Toilet Slope

Waste from a toilet will not flow properly with the wrong slope in the line.

A properly sloping toilet line ensures that all the waste moves down to the sewer without getting stuck and causing a stink. The ideal slope is 1/4-inch down for every foot of run. Use this to determine how far down the toilet drain pipe should go before it ties into the vertical soil stack line.

Things You'll Need

• Measuring tape
• Marker

Instructions

1. Measure the distance in feet from the toilet to the soil stack line.

2. Multiply the number of feet in distance by 1/4 inch per foot to find the number of inches the pipe should drop over the run. For instance, if the soil stack line is 4 feet from the toilet, the pipe should drop 1 inch because 4 feet x 1/4 inch per foot = 1 inch.

3. Mark the spot on the soil stack directly across from the opening of the toilet drain.

4. Measure down the soil stack the number of inches of calculated drop for the pipe. This is where the 3-inch-diameter toilet drain line will meet the soil stack for drainage to the main drain and out to the sewer.

References

• Mastering Math for the Building Trades; James Gerhart
• Plumbing a House; Peter Hemp
• The Illustrated Home; Carson Dunlop