Thinking Septic? Don’t Get Stuck in the Outhouse – Get a Perc Test First!
March 28, 2018
If you’re looking to build on a property that doesn’t have access to a public sewer system, the seller may have already disclosed the fact that you’ll need to install a septic tank. Before you sign on the dotted line, be sure to request a perc test to make sure that a traditional septic system will work on your property. Here’s why:
Septic tanks basically work by collecting your waste, using bacteria to break it down to liquid form and then distributing the fluid into the surrounding soil. (This is why the grass above your septic tank is so inexplicably green!) The whole system hinges on the soil’s ability to absorb liquid at a specified rate. If your soil can’t absorb the liquid fast enough, pull out the boots and pinch your nose. You WILL notice.
How a Perc Test Works
Before you can even consider building a septic tank, you’ll need to identify a spot on the property that has at least two feet of good soil from the base of the drain channels to the stone or to the water table below the surface. In Florida, you should be particularly careful for low-lying areas that may be too close to the water table.
Next, your contractor will need to test the exact rate at which your soil absorbs fluid. The passing rate of the peculation test varies municipality. The two commonly used tests that determine a site’s soil suitability are the soil evaluation test and the already mentioned perc test. Do not forget to first have a talk with the health officer of your area to get informed about the particulars of these two tests.
Soil testing
Generally speaking, soils with a high clay content or soils with a lot of solid rocks are the most likely to fail the prec test; whereas those with a high gravel content perform the best. Most soils fall somewhere between these two categories. Before you go all in, you can do an unscientific test onsite to see if the project might be worth perusing. Dig below the topsoil to the lighter soil beneath. If you can grasp a handful of damp soil and move it into a level shape that holds together, that’s a good sign.
Your contractor will dig a hole 7 to 10 feet deep to collect soil samples. This test mostly aims to determine the draining characteristics of the soil. While most soil specialists trust they have enough data to plan a suitable septic system, most states require perc testing as well, to quantify the rate at which water permeates through the dirt. The outcomes of this test show if the town will enable a septic framework to be introduced, and framework designers utilize the outcomes to estimate the drain field.
Perc Testing
Before you begin a perc test, gather the necessary info from your town health officer concerning the number and depth of holes, the appropriate time for the test to be done and the absorption rates needed to pass the test. The general process goes something like this:
- Dig at least two holes with a diameter of 6 to 12 inches and a depth between 2 to 3 feet.
- Deposit 2 inches of gravel on the bottom of the holes.
- Soak the holes well. Keep watering them for at least 12 hours so the hole has 12 inches of water during this period of time.
- The following day, remove any loose soil that has fallen into the hole and add water so that it reaches 6 inches above the gravel.
- Finally, measure how much the water drops in exactly 30 minutes. The number will determine the percolation rate, that is the time the water needs to fall 1 inch. The ideal rate is 60 minutes per inch and the maximim rate varies between 30 to 120 minutes per inch.
What If Prec Test Fails?
Particularly in rural areas a failed percolation test means you can’t build, so be sure to ask BEFORE you sign on the dotted line.
In more populous areas, you’ve got a few options. For sites with high water tables, you might have the capacity to de-water the filtering zone by deliberately putting rock filled trenches and subsurface deplete pipe to lead water far from the deplete field. You may need the help of a civil engineer or a geotechincal expert to assist you in this case.
Ask your contractor about other, non-gravity-sustained septic systems available in your area. While they can cost a bit more and require quite a bit more equipment, it might be a small inconvenience compared to the opportunity to build your dream home on that perfect piece of land. Consider asking your seller for a concession to help cover the cost.
When it comes to your dream site, no obstacle is too great a challenge, especially with the right partner. When you’re ready to buy your perfect parcel, see how Steven Jantzen can help you.