What Happens If My Installer Hits a Septic Tank Mid-Patio?

You have a price in hand and a start date on the calendar, but one thing occurred to you. What if the crew digs down a couple feet and finds something you didn’t know was there? That’s a legitimate concern. You’re spending good money on your backyard, and the one part of the job you can’t see has the potential to change the price quite a bit.

My name is Randy Thompson, and I am the founder of All-Out Hardscapes LLC. We build patios, walkways, and outdoor living spaces across Savannah and the Coastal Lowcountry, from Wilmington Island and Savannah Quarters out to Pooler and Richmond Hill, and we have installed more than 150 projects in just over ten years. I am a certified Techo-Bloc Pro installer, which is a manufacturer certification you only earn by training on the material and building to the manufacturer’s standard.

So here’s what I have learned after a decade of digging in this Georgia ground. Most of the time we are going to hit something. It’s not always a septic tank. Sometimes we find an old irrigation line, a buried stump, or the slab from a shed that hasn’t been there for 20 years. The big question isn’t whether your yard has a surprise in it. The most important question is whether the person who quoted your job planned for that before they gave you a price.

What Happens the Day My Installer Hits One?

When we hit something, the digging stops in that part of the yard. That is the first move, and that’s actually more important than it sounds. You never want to keep pushing the machine to see how bad it is, because that is how an abandoned tank collapses and a live tank becomes a huge mess in your grass.

From there it is three questions that come in a certain order. What is it? Is it live or abandoned? And where does it sit relative to the patio we are building? We hand-dig enough to answer all three before anybody guesses at anything.

Then you get a change order, which is a written update to your price and your timeline when a job has to change after the contract is signed. It lists what we found, what we have to do to deal with it, what it costs, and how many days it adds to the project. Nothing gets covered back up on the down low. We only go back to work once you see it and approve it.

Why Is There a Septic Tank Under My Yard That Nobody Told Me About?

Because a lot of houses around here were on septic before the sewer line ever reached the street. A septic tank is a buried concrete or fiberglass box that holds household wastewater and lets it settle before the liquid moves out into a drain field. The drain field is a bunch of buried pipe and stone that spreads it into the soil. When a house got tied into city sewer later, the tank didn’t always get dug up out of the ground. Plenty of them were pumped, filled or crushed, and just left there.

Then the house sells a couple times and every time it changes hands, a little more of that history ends up not being on the paperwork, until the current owner has a beautiful backyard and no idea there’s an old septic tank under their grass. The seller didn’t hide it from you. They probably had no idea it was there either.

People usually assume that a utility locate service covers this, but it does not. Calling 811 before a dig only marks the gas, power, water, and communication lines up to your meter. Whatever is on your side of that meter is private, and nobody comes out to mark it. The old tank, the drain field, the dog fence, the irrigation line that the last owner put in himself are all mysteries. Having the location of utilities marked is a good idea for every single job. But just know that it’s not a foolproof map of what’s under your yard.

Can They Just Build My Patio Over the Top of It?

No, and you should understand why because building over it sounds like the cheap way out, but it’s actually the expensive one.

A patio doesn’t sit on top of your yard. We dig the yard out and build a base down in that hole. It’s an open-graded stone base, which means clean crushed stone with the fine dust screened out so water runs straight through instead of sitting in it. Ours is four inches of #57 stone under two inches of #789 chip stone, compacted in one single firm pass, with no sand anywhere in it. That compaction is the whole reason the patio is still flat decades from now. So we are running a plate compactor and a loaded machine back and forth across that ground, and an old septic lid was not designed to withstand that. It was only engineered to hold dirt and grass on top of it.

Then there is the issue of access. That lid is the only way into the tank. If you pave over it, you haven’t solved anything. You’ve now put a finished patio between a service truck and where it needs to reach. The first time somebody needs in there, part of your patio has to be torn up, and it’s always your favorite part of the patio.

And even if the tank were crushed and filled where it sits, you would be building on disturbed ground. Fill that has been dug up and put back always settles after the fact, and a patio built on it settles as well, which causes cracks and other issues. It might take a few years for that to happen, and there are no warning signs from the surface.

So there are really only two ways to deal with it, not three. The tank comes out, or the patio location is changed. Moving the patio is a design thing, it doesn’t mean the project comes to a halt or that it can’t be done. Shifting the patio a few feet, doing a curve where you had a straight edge, wrapping a seat wall around the far side. That is actually the part of this work we enjoy most, and it’s why we personally design every job instead of dropping a rectangle in a yard and calling it a patio.

What Does a Buried Tank Do to My Price and My Schedule?

Every trade that digs prices its work based on what they saw when they came and looked at your property. That goes for us, for the pool crews, for the guy setting your fence posts, and any other trade that has to dig. Unknown buried objects are the most common reason a dig job changes price in the middle. If anybody tells you differently, they haven’t dug enough holes.

So we want to be very clear about what a patio quote actually covers. It covers the patio, which means the excavation, the stone base, the pavers, the joint sand, the edge restraints, and hauling off the dirt we dig out. It does not cover removing something buried that nobody knew existed, because nobody can price out what they don’t know is there.

A few factors decide what it costs when we do find something buried. How big the tank is, whether it’s live or abandoned, where it sits in relation to the patio, how much concrete and saturated soil has to be hauled off, whether the design shifts to work around it, and whether the hole needs clean fill to replace what came out.

Here is one of ours, so you can see the actual numbers. We quoted a two-week job at about $26,000. It turned into about $32,000, because an unknown septic tank sat in the middle of the patio and all of it had to be removed. That’s just how these jobs go. But that is an example of a real job, with a real price.

The schedule is the other half of this. Most of the time we are going to hit something, so we factor in an extra week into the timeline from the get go. We believe in under-promising and over-delivering. That week is not padding we are hoping to keep. It’s extra built in time that allows for a tank to come out without your project spilling into the next month unexpectedly. It also keeps us from having to rush things just to finish on time. Rushing the base is how a patio fails in three to five years. We would rather hand the week back to you than take it out of the part of the job where it can actually cause issues later on.

How Do I Keep This From Being a Surprise on My Job?

You cannot predict what’s under your yard. You can mitigate the potential for damage though. Before you sign anything, do these four things.

• Tell whoever is quoting the job everything you know about the property, including whatever the last owner told you.
• Ask your county about septic records for your address, because older systems are sometimes lacking paperwork.
• Walk the yard yourself and look for signs like a rectangle of grass that greens up differently from everything around it. Maybe there’s a low spot that stays soft for days after rain, or a concrete cap or metal lid sitting just under the sod, or an old cleanout pipe standing near the foundation.
• Ask the person quoting you whether he walked the property himself, and how the price and schedule changes if he hits something when digging.

That last question usually tells you what you should know about whoever is building your patio. It’s also why we evaluate before we quote, instead of pricing a job using only a satellite photo and a phone call. We personally walk your yard, we look at where the water goes, we look for the signs, and we design to what is actually under there.

When Does a Buried Tank Not Change My Project?

The tank only matters if it is in the way of the build. If your house is on sewer and the old one sits off to the side of where the patio is going, it can just stay there and your price doesn’t change. If your system is live, documented, and nowhere near the patio, none of that affects the job. We are definitely not looking for a reason to jack up the price on a job.

And if you already have a patio sitting on top of a tank, you’ll have to talk to a septic contractor and the county, that’s not a patio issue. We build outdoor living spaces. We are not a repair or diagnostic company, and we are not going to pretend otherwise just to get a foot in the door.

We will be very upfront about the money part. We are not the cheapest company in this market to install your patio. If you’re just putting a small patio in a documented yard well away from the house, and someone quoted you a few thousand dollars less than everybody else, that might be the way to go. Just read what it says about unknowns before you sign anything. A quote that stays silent on the subject is not the same thing as a quote that covers it.