If you are building a new home in an area that does not have a sewer system, testing of the soil is required to determine if a lot is buildable or not. This testing is called a percolation or perc test. Some use the phonetic spelling and also refer to this as a perk test. A perc test is usually conducted by a private company under the watchful eye of a city or town's Board of Health Agent or Building Inspector. The agent or inspector will then determine if the property passes or fails the perc test.
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What is a percolation test
A percolation test measures the amount of time it takes for liquids to be disbursed through soil. This is important because it determines whether the property can accommodate a leaching field where effluent from the septic system will be directed and released back into the ground.
Dig Several Holes on the Property
Depending on where you live will determine how many percolation test holes need to be dug on the property. Typically the number is around three holes, but could be more or less depending on the size and scope of the building project, and where the leaching field is to be located.
Pour In The Water
After the holes are dug to the required depth, they are filled with water at several intervals. Then the time it takes for the water to dissipate into the ground is measured at a per-minute rate. Depending on the rate of dissipation, percolation tests can take a few hours or all day. The per-minute dissipation rates are recorded by the company and the health agent or building inspector determines if the soil is proper for a leaching field.
Pass or Fail
Water that runs too quickly into the ground indicates the soil could be too sandy to accommodate a leaching field, as this would translate into the effluent from a septic tank being released too quickly back into the ground and not giving it a chance to be "filtered." Likewise, water that does not dissipate into the ground or does so at an extremely slow rate indicates the soil is non-permeable and could result in a septic tank backing up or causing the effluent to surface and pond on the property, which would be a health violation. In the event of a perc test failure, the property owner should investigate alternatives, depending on the health regulations of their city or town.
Timing and Costs
Percolation tests are typically conducted during a region's wet season, usually February through April; however, they can be conducted all year round if your city or town has adopted this provision. Percolation tests are not inexpensive and cost anywhere from £65 to several hundred dollars depending if your location charges per hole dug or per house lot.