How to calculate concrete thrust blocks

Updated July 20, 2017

Pipes are used to safely contain and transport materials from one point to another, particularly in the water and sewage venues. In order to move material through pipes, the pipes must be pressurised. It is possible for the sections of pipe to separate under the amount of pressure required to move materials through them. This separation can be avoided with the use of concrete thrust blocks, but you need to know exactly how much area the thrust blocks need to cover.

Determine the thrust value by multiplying the internal pressure by the square of the outside diameter by the mathematical value π (pi) by one quarter (0.25). The internal pressure should be measured in pounds per square inch (psi).

Divide the thrust by the allowable soil bearing capacity, measured in pounds per square feet. The allowable soil bearing capacity is a regulated standard charted by your local municipality. It varies depending on the kind of soil, sand or rock that the pipes travel through.

Multiply the quotient by 1.5. The result is the necessary area that your concrete thrust block must cover, measured in square feet.


The quotient is the result of dividing one number by another.


Check with your local building code authority to determine any special regulations covering concrete thrust blocks.

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About the Author

Tom Fritchman is a freelancer who has been writing professionally since 2009. His first writing credit was actually a stage play called "Window Watching" performed at the Northmont Auditorium in Clayton, Ohio. He holds a Bachelor of Arts in language and literature from Wright State University.