What's a Perk Test and Where Do I Get One

If your new custom home project is for a residence where your lot is not connected to a public sewer system, you will need to put in your own underground sewage waste disposal on your property, usually referred to as a septic tank. The first time this came up was when I went to get my lot loan, I was asked for a perk test and water report. Not sure where to turn, I started making phone calls.

At first I thought that I would need a soils/geotechnical engineering firm. I couldn't reach one immediately so I used google maps to find a nearby septic service company. Steve at ABC Septic service was very friendly and gave me some direction. Steve explained that in Idaho, I would actually need an excavation company to dig a hole 12 to 15 feed deep with the inspector there. Since he does not do installations or excavation, he referred me to Phil at Bulldog Excavation.

Phil does perform the excavation for perk tests, but that the department of health and welfare is the agency that manages the building and maintaining of septic systems. Phil was great, giving me a ballpark estimate for all the excavation that I would have to do. We talked about the road that I would need to cut to the building pad, the pad itself for a daylight basement, the water, power and the septic. His initial estimate for everything was about $15,000 or less. This is the number I put on my planning worksheet, so sounds like it will be in budget if I have the whole job done by the excavator.

Next I called the Central District Health Department. This department is responsible for all kinds of things including overseeing day care centers, restaurants and of course, sewage disposal. The person I talked to explained the process for getting this inspection in a speculative situation like mine, where I have an accepted offer for the property, but I am doing my due diligence to ensure no problems will occur in building the home. In this area, I will need to submit a request for an onsite inspection for a "Speculative Site Evaluation."

The cost for this kind of "pre-permit" is about $358, and I have to provide the excavation to dig the hole used in the inspection. If I do move forward with the full septic permit, this money can be applied to the actual permit for the difference. A septic building permit from Central District Health is $721. If I don't "upgrade" to the full permit within the first year, I can extend the permit for another year for $93. So that will give me plenty of time to finalize the plans.

I downloaded the permit form in .pdf format for printing from the Central District Health web site (.pdf form) and filled it out on paper. Part of the process was to create a plat map of where everything would be located. You will see on the downloaded form instructions for the diagram, and they provide a place to illustrate it. I created my map on google map engine. This is a cool drawing program for maps where you can create map layers and add objects such as property lines, building location, road locations and your proposed septic system. Try it out at https://mapsengine.google.com/map/.

Here is a picture of my plat map initially created with Google Map Engine:

I put my initial plat map on paper:

The form was not hard to fill out, but did have a few things you might not be sure on yet. For example how many square feet is the house, and how many bedrooms. I don't have all those details, so I put initial estimates. So once my request is submitted, I should be able to schedule my "perk test" with the inspector, and pass that along to the lender.

Wait, there's more:
I learned this before going through with the perk test with the excavator: During the loan phase, you will probably be able to use an existing perk test that is on file with your planning and zoning department. I submitted the existing engineering report to my lender and so far they have taken it. So, you may not need to do this test unless you are developing a subdivision. Find out what is needed by your lender.