What is a Percolation Test?
If you live in Western Massachusetts, then you’ve no doubt seen many property listings with septic systems, or may even be the owner of one; it’s a common facet of our relatively rural living. When you buy property to build a home in the countryside, you typically do so because of the relative isolation country living provides. However, with that isolation comes plenty of challenges.
One such challenge is your sewer system. In many rural areas, there is no city sewer, which means you’ll need to utilize a septic system. However, you can’t put a septic system just anywhere. Before you dig a hole for your brand-new septic tank, you’ll need to perform a percolation test or “perc test.”
Why is a Percolation Test Needed?
To put it simply, a percolation test is needed to determine how the soil surrounding your prospective septic tank drains. Soil that can’t adequately handle groundwater water over a set period will inevitably envelop your tank, flooding it, and in doing so will contaminate the surrounding groundwater with sewage. It’s easy to understand why you wouldn’t want that.
A percolation measures the minimum and maximum rate at which water is absorbed by the surrounding soil. You want soil that strikes a careful balance between absorption and drainage.
How is a Percolation Test Performed?
A percolation test is simple by design but requires expertise to truly measure and understand. You may be wondering, “how do I pass a percolation test?” During a perc test, we do the following:
- Find a spot to dig a test hole approximately 300mm wide and 300mm deep beneath the “invert level” of wherever the septic outlet pipe would start
- Saturate the soil with water, typically overnight
- We ask you to check this hole a few times during the day; refill if needed
- If the hole continues to drain multiple times, then you already know that the absorption rate is too low for a septic tank, but we will clarify this for you when we return
- The next day, we’ll refill the hole with water, since it should be saturated, we can time the soil absorption rate; we measure how long it takes for the water to decrease to the 75mm line within the hole
- The time this process takes is divided by 150
- This value is your percolation value number
- We repeat this process up to 3 times for accuracy and consistency
What Happens if I Fail the Test?
The percolation value needed to establish a septic system is set by the Health Department, so if you fail the test, you typically need to explore other areas for your system.
However, if you fail a perc test because your soil drains too slowly, you typically have more options than if your soil drains too quickly. Slow-draining soil may be fixed through the excavation of a dam or trench, or by installing some sort of drainage system on the property. To put it simply; you want to be able to move excess groundwater away from your septic system at an adequate rate.
Call Excavation Plus Inc. for Your Percolation Test
If you plan on building your home on a property that is outside of municipal sewer, then ensure you do your due diligence and order a percolation test before it’s too late. We offer percolation testing that is thorough and will ensure your home build will stay on track.
