Onsite Sewage Treatment Program

Plastic Limit

Definitions

Plastic Limit (PL or wP) – The minimum water content at which the mixture acts a plastic solid.

Procedure for Determination of the Plastic Limit

1.Select a handful of soil for testing.

2. Roll the sample between the palms (in the shape of a pencil).

3. Continue rolling the thread until it reaches a uniform diameter of 1/8 in (if possible).

4. If the sample does not reach a diameter of 1/8 inch the soil is above the plastic limit and construction can proceed.

5. If the sample is rolled into a diameter equal to 1/8 inch then the soil is too wet and construction cannot occur

For More Information

Visit our web page at http://septic.umn.edu for information.
The Septic System Owner’s Guide is an excellent resource. To order, call 800-876-8636 or go to http://shop.extension.umn.edu. University of Minnesota Extension web site: http://www.extension.umn.edu.