What the Heck is a "Perc Test" (and How Much Does it Really Matter)?

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Added 4 years ago by tomm

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See the full blog post here: https://retipster.com/perc-test

If you're dropping some serious cash on a parcel of vacant land, there is one issue that may seem insignificant at first glance, but it has the potential to make or break a land deal.

The “Perc Test”

A Perc Test (also known as “Perk Test”, and more formally known as a Percolation Test), is a soil evaluation that tests the rate at which water drains through soil.

Perc tests are required in just about every civilized municipality in the world – because the results of this test provide crucial information required to design and install a septic system.

A perc test is conducted by drilling or digging a hole in the ground, pouring water into the hole and then observing the rate at which the water is absorbed into the soil. In most cases, properties can easily pass a perc test when the soil has higher concentrations of sand (because sand tends to absorb water at a much faster rate than clay or silt) and when the property is situated in an area with a low water table.

Why is a Perc Test Necessary?

For all intents and purposes, a perc test (and subsequently, a septic system) is only necessary when a property does NOT have access to a municipal sewer system.

If a vacant lot is situated within reach of an existing sewer hook up, this will usually eliminate the need for a septic system altogether. For this reason, the availability of an existing sewer system can be big "perk" (no pun intended) when evaluating a property's suitability for building a dwelling of any kind.

When there isn't an existing sewer system nearby, that's when you'll need to explore the feasibility of a septic system. In order to determine if a septic system is possible, most county health departments will require a perc test.

Most of the world's septic systems are designed in a way that requires a septic drain field or "leach field" to drain away any excess water. When solid waste settles in a septic tank, the excess waste water is then discharged into the septic drain field through a network of perforated pipes.

The contaminants expelled from this waste water are then trapped and eliminated in the soil. This happens primarily through the process of percolation – and also through evaporation, transpiration, consumption by plant roots and eventually, the remaining water re-enters the ground water and/or surface water.

The typical size of a drain field is determined by the expected volume of waste water to be discharged from the septic system (which is usually estimated based on the size of the proposed building).