Perc Tests and Soil Analysis in Land Investing - Common Practice or Optional?

Hey everybody. Do any of you get a soil analysis when you buy? I have a land realtor that says all his land investors get them. I just got a bad one with the suggestions being to use a shallow or ultra-shallow system. The realtor said it is very hard trying to sell when the buyer knows they have to get an alternative system. Some investors I talk to say they always get them, some say they do for smaller parcels and some say they never do. One guy said every buyer he gets ask whether he has one or they won’t to one or a perc test. How do you all handle this?

@carolinajay it’s a good question. Perc tests are one of those things I’ve always been a little torn on. On on hand, if you’re in an area where septic drainage is a concern, and if it matters whether the future buyer can build something on it (it usually does to some extent), then yeah, it is something you should be pretty certain about before you close on it.

If you have a trained eye, and use the wetlands mapper, USDA soil maps and look at other clues, you can usually get to 80% or higher certainty about the situation between those things. I usually don’t spring for a legit perc test unless I’m paying a darn high price for it and I know the perc test matters.

Keep in mind, sometimes it literally doesn’t matter at all. When I bought my self-storage property as vacant land a couple years ago, I paid full market value, and I still didn’t get a perc test. Why? Because it didn’t matter. There wasn’t going to be any plumbing on the site… so you really just have to think about how much you’re paying, what the likelihood of problems is in the area, and what your intended use is (or your future buyer’s intended use).

I think most people can get comfortable shrugging it off and not doing it if they’re paying south of 40% of market value… but again, you just have to weigh the risk of what the property’s FMV will be if you suddenly can’t use it for that purpose. Sometimes it’s catastrophic, and sometimes it doesn’t matter at all.


@retipsterseth I just did the soil analysis, not the full test. Got suitable soil for a shallow conventional system. Just farther up in the soil and you have to add another layer of soil. Soil guy said about another $2k. I would go back to him if I needed the full test because he’ll do it much faster than the county. He’s a Licensed private soil scientist. That way I can control what’s going on. Thanks for responding.

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@carolinajay good to know. What’s the difference between a soil analysis and the full test?

@retipsterseth The analysis is when they go out and test if the soil is suitable for septic by the composition of the soil. Alot of investors I know sell with this. More than likely, if the soil is composed of wihat is normally deemed good for a septic system, it will pass a perc test. It’s little more to it than that, but that’s close.This was my first one so I don’t know everything about them yet. They are cheaper also. $500-$1000, usually. Mine was $800. You’ll get a report that you can attach to your listing. My realtor works with alot of investors and he said the analysis is good enough with buyers about 75% of the time. It’a always a few that want the full test.

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@carolinajay interesting. So, the analysis just tests the soil type, whereas the full test is when they pour water into it and observe the rate at which it drains. Am I understanding that right?

@retipsterseth I called him so he could explain it to me so I could tell you better. It’s still borings happening but it’s not what a full perc test was back in the day. The report is basically his opinion, as a licensed professional in the field, as to the suitabilty of the soil for a septic system. He said they haven’t done the perc test, at least, here in NC in years. He said it is some more in-depth test him or the county can do. He has other licenses where he can design and authorize construction of the system. He’s also a waste water evaluator so he can do everything the county can, almost. With him, county never has to get involved until right at the end to ok everything that was done during construction. One of his land guys goes a step further and gets the permit for the site ($1400) and uses that as a selling point with his flips.

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I’ve been burnt with properties that dont perc. Its not fun. I still don’t get tests on all properties I buy. Helps to see other homes in the same soil near the property for confidence. When I work an area I have done deals in before I can email my soil guy before I buy and ask him to review maps and give feedback he does it pretty quick. I also only do the soil test for 5-600 bucks because allot of the time you need to know exactly where ‘you’ plan to build because the usual chain of events is to get a perc site where you plan to build then someone from the county evaluates and actually puts the stamp on how many bedrooms it will perc for, sometimes they even want build plans for the site. So when I am marketing I say a liscensed soil scientist has identified a soil site for septic and leave it at that to give the buyer confidence and then explain that it has not perc’d for specific bedrooms as I don’t want to assume where someone wants to build on a property and they seem to get it.

@landexitadvisors are you guys familiar with the soil maps from the USDA? They’re free to use on the USDA website, and you can also see the same maps as an overlay in Land id, if you use that.

I just made a video where I touched on this at around 7:56.

Knowing the soil types in the area can give you another clue as to how likely the soil will be to drain water sufficiently.

These maps aren’t the same as doing a legitimate soil test. Similar to the federal, state, and county topo maps, they’ll give you a rough idea, but they aren’t meant to be pinpoint accurate.

That said, I had a soil test done recently on one of my properties, and the soil we found was exactly the same as what these soil maps told us we’d find… so, they’ve been pretty accurate in the few times I’ve put them to the test.

Soils that drain water quickly usually have larger particles, like sandy soils. Sandy soil has large, coarse particles, so water can move through it pretty fast. This makes it great for quick drainage but not so great for holding onto water and nutrients.

Soils that might cause problems in a perc test are those with smaller particles, like clay soils. Clay has tiny particles that stick close together, making it hard for water to pass through. This means clay soils drain very slowly and can cause issues in a percolation test. They’re great at holding onto water but not so good at letting it go quickly.

@retipsterseth Thanks for the reminder, I have not incorporated using this in DD but need to going forward. Will bookmark.

So some counties have a GIS system that will pull up the perc test AND actually show the layout of the leach lines (they almost always follow the contour of the land) and how many feet of leach line the property will need for the house that is built on it. When you have houses close the parcel you are considering, you can pull up this information and see the exact numbers. You also have to know in your area how big a parcel generally has to be to safely get all the lines in. It can be as low as .28 of an acre for a two bedroom house. I do not get a perc test as I let the builder/home owner do that and I write into the contract that if they drop out of escrow, then they must supply a copy of the perc test to me so I can see what the results are and then I don’t have to pay for the test. Sometimes builders will drop out of escrow because they thought the property could support a 3 bed home and it percs for only a 2 bedroom. That’s fine by me because someone will come along that is OK with building only a two bedroom home. Not a problem. On the septic report the soil engineer will say something like, "based on the size of this property, the property may be able to support a 2 bedroom house assuming 320 feet of leach line. Some people say that a property “passed” or “failed” a perc test. This is a misnomer in my opinion. There is no pass or fail box on the report. It simply reports what the capcity of the soil is to disperse liquid and how much leach line will be required for a 1, 2, 3 or 4 bedroom house based on the numbers generated by the perc test. Whether all the leach line can be fit into the confines of a particular property is usually a decision made by a builder. And there’s this also: the county can come along after the perc test is done when it is doing its permitting and dispute the numbers. It’s the county that has the final say as to whether the perc test holds any water or not (pun intended). So that means that a perc test only mitigates risk as far as you can go, but it never eliminates the risk. Hope this helps.


@landexitadvisors That’s exactly what I’m talking about.

@herrbshaw As far as using online sites to look at soil reports/overlays, Land id matched up, perfecty, to my soil guys analysis. I don’t trust it 100% of the time, though.