What is a Perc Test?

A percolation test or “perc test” is a test to determine the absorption rate of soil for a septic drain field or “leach field”. The results of a percolation test are required to properly design a septic system. In its broadest terms, percolation testing is simply observing how quickly a known volume of water dissipates into the subsoil of a drilled hole of known surface area. A perc test can take anywhere from 6 to 48 hours to complete.

Before doing a percolation test, an exploration hole is excavated to examine the soil layers and determine which layer will best suit the drainfield. One or more holes are then bored to a specified depth in the soil layer of the proposed drainfield, soaked for a period of time, and then left to swell. The final test is then conducted by filling the holes to a specific level and timing the drop of the water level as the water percolates into the surrounding soil. When the water starts to drop at a stabilized rate the test is complete. The percolation test results indicate how large the septic drainfield should

Why Choose AOS?

AOS conducts hundreds of perc tests every year and we have a solid knowledge of Utah’s diverse and sometimes difficult soils.  We do all of our own excavation and soils work to ensure that the percolation test is conducted at the perfect depth and soil layer to get the best results.  A perc test done improperly will result in:

1. An oversized drainfield, which could cost thousands of dollars.

2. An undersized drainfield ,which could result in system failure.


3. A failed perc test, which could deem your property un-buildable.

This is why the percolation test is so critical and should not be done carelessly.  Don’t turn over your investment to just any guy with a backhoe!  Go with a trusted company that specializes in septic systems and has the experience and education to do the job right.  Remember that saving a few hundred dollars up front can cost you thousands down the road.