If you're planning to build on a rural parcel, the percolation test is one of the most important pieces of information you can have before you close. A parcel that fails a perc test isn't necessarily unbuildable, but your options narrow and your costs go up. Here's what the test actually measures and how to factor it into a buying decision.
What a perc test measures ¶
A percolation test measures how quickly water moves through the soil at a specific depth. The result tells you whether the soil can absorb the effluent from a conventional septic system. In Wisconsin, the test is conducted by a licensed soil tester who digs test holes, saturates the soil, and then measures the drop in water level over a set time period. The result is expressed as a rate: minutes per inch. A rate under 60 minutes per inch generally qualifies for a conventional system.
What happens if the parcel fails ¶
A failed perc test means the soil doesn't drain fast enough for a conventional septic system. That doesn't necessarily mean you can't build. Mound systems, which elevate the drain field above the natural soil surface, are approved in Wisconsin for sites that fail conventional perc. They cost more to install, typically $15,000-$30,000 versus $8,000-$15,000 for a conventional system, and they require more land area. Some sites fail even for a mound system, in which case a holding tank or connection to municipal sewer (if available) are the remaining options.
How to handle perc testing in a purchase ¶
If a parcel you're interested in hasn't been perc-tested, you have a few options. You can make your offer contingent on a passing perc test, which is common and reasonable. You can commission the test yourself before making an offer, which costs $300-$600 in most Wisconsin counties. Or you can factor the uncertainty into your offer price. At Pine Zone Land, we note in every listing whether a perc test has been completed and what the result was. If it hasn't been done, we say so.
Timing and county requirements ¶
In Wisconsin, perc tests must be conducted when the soil is at or near saturation, which typically means spring or after a significant rain event. Tests done in August on dry soil may not reflect actual conditions. Some counties require that the test be conducted by a certified soil tester and that the results be filed with the county sanitarian's office before a building permit can be issued. Check with the county before you assume a test result from another state or an uncertified tester will be accepted.
If you have questions about a specific parcel's perc status, that information is in the listing or Marcus can pull it for you. Call +81 42-541-6283 or email info@pine-zoneland.com.