A very important question that needs to be asked when buying property for your new custom home is, “does it perc?”. If the property is going to have a septic system instead of city sewer, not asking this question might cost you thousands of dollars! The problem with this question is, few people know to ask, and fewer know what it even means. It is an easy test to get and most of the time the land owner that is selling the land will order it and pay for it.
What is a Perc Test?
A perc test, or percolation test, determines the absorption rate of the soil in preparation of building a drain field. In other words, will the water from your drain field be absorbed into the ground or will it just sit in the drain field and overflow? The absorption rate will determine what type of drain field will need to be constructed and how big it will need to be.
How is a Perc Test Done?
A basic perc test is two or more holes dug at least 40ft apart in a proposed drain field area. They are filled with about 6” of water, then a yard stick is placed in the hole. The water is then timed to see how many minutes per inch (MPI) is absorbed into the ground; this is usually done with a 30 minute test. This is a very basic explanation of a perc test, as it varies from county to county, but I think it paints the picture for you. An average cut off limit for a standard drain field is 60 minutes per inch, but can vary between 30 and 120 minutes.
Who performs a perc test?
Usually the county is in charge of the perc testing. The environmental health department is the one to call. Remember that there is only certain times a year that would allow for an accurate perc test. Once called and payed for, a representative of the office will then come out and perform the test and get back to you within 10 days with the results.
What if the Land Fails?
If the perc test fails for a standard drain field, there are typically other options, but that is where it may cost thousands more than a standard system. There are a few different grades of septic systems - Standard Gravity Drained System, Raised Mound, Pump and Float System, and Engineered System(s). Each one is more expensive than the latter and the maintenance and requirements go up with the price. (There are other systems that are not listed here as well but these are the more common systems used).
Is a perc test good forever?
This is a question that many people do not know the answer to. I have asked the “does it perc?” question many times with the answer of “yes”. I will throw the curve ball question of “when was it tested?” after their answer, in which I will get the response of “when we bought the property 15 years ago”. That is an answer that I cringe at because so many people have no idea that a perc test actually does expire. Typically the perc test is good for 3-5 years; here in Michigan it is 5 years.
I don’t write this to scare anyone from buying land that is going to have a septic system, but to make you a more educated buyer if land ever becomes available to you to build your dream home on. If you gained nothing from this article, PLEASE, just remember to ask for the perc test or make your offer on the property contingent on a passing perc test. This is a basic “Perc Test 101”, not an in-depth article, and it is meant to give you a basic idea of perc testing, not to become an expert perc tester.
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