For all intents and purposes, a perc test (and subsequently, a septic system) is only necessary when a property does NOT have access to a municipal sewer system. If a vacant lot is situated within reach of an existing sewer hook up, this will usually eliminate the need for a septic system altogether.

Why do I need a percolation test?

Perc tests determine the right and wrong locations for a septic system, and they're often required by local jurisdictions before a new one can be built or an old one replaced. That's because septic tanks work by holding wastewater long enough to naturally separate liquids and solids.

Can you do your own percolation test?

If you're planning to install a new septic system, local ordinances will require you to conduct a soil percolation test. In some jurisdictions, you can do the test yourself, but in others, including some parts of California, you need a qualified professional to do it.