All About the Percolation Test Required for a New Septic Tank

Septic systems allow you to build a home or business on even the most remote properties far from existing sewer connections. However, determining if a septic tank will work for a specific property requires more than just the owner's willingness to pay for one.

A percolation test, also commonly abbreviated as a perc test, is required before your county will approve a permit for the installation of the system. Learn all about this test before it's performed so you're prepared for the process.

What Is the Purpose of the Test?

A percolation test shows how well the soil in a particular part of the property drains. Septic systems rely on a drainage rate that isn't too fast, which lets waste escape before it gets a chance to break down, or too slow, which causes the tank to fill up and overflow.

You may need multiple percolation tests to find the right location for a septic tank. Each test will only show the percolation speed of the soil in one particular area, and an open spot a few dozen feet away may have completely different properties and therefore different test results.

How Is Percolation Tested?

Percolation tests vary slightly depending on the type of system you want, but they all have a few basic components in common. All of the tests involve digging a hole of a certain depth, filling it with water, and measuring how long it takes for the water to completely drain into the surrounding soil.

The shape and layout of the hole varies, but it usually must be dug to a depth of anywhere from 4.5 to 10 feet. Shallow holes won't accurately measure the water absorption rate of the soil. Even if a shallow pit drains at the right rate, deeper layers of soil might interfere with the septic system's drainage.

Contractors usually dig at least two pits at opposite ends of the proposed system to ensure the entire area will drain at an acceptable rate.

When Do You Need It?

Most percolation tests are done before the installation of a new septic system. However, they're occasionally also used if there's a problem with an existing drain field and the company handling the repairs needs to know if soil qualities are causing the problems. Relocating a system also requires a percolation test in some cases since the new location could have different soil drainage characteristics.

Who Can Perform the Test?

You can dig your own percolation test pit if you want to save some money and learn about your property's drainage before paying for any professional work. However, a homemade percolation test won't help you get the permits needed from your county, so you'll still need an official test.

If you try digging your own pit, slope all of the sides to both prevent collapse of the surrounding soil and so you can exit the pit if you fall into it. Professionally dug pits only require one sloping side, but they're created with large machinery that creates relatively stable sides. When you're doing the work by hand with a shovel instead, sloping all four sides is safer.

What Happens If the Test Fails?

Failing a percolation test means you can't build a traditional septic tank in the area you tested. If you test all of the viable areas on the property and can't pass any of them, you can still choose from many alternative septic and residential sewage treatment systems that are designed to work in areas with poor or fast soil drainage.

Schedule your professional percolation test today with us here at Walters Environmental Services to discover whether your property can support a septic system or not.