Are you thinking about putting an addition on your existing home? Or have you found your dream home but the only thing it’s missing is a swimming pool? Before you start hiring contractors, one of the first calls you’ll need to make is to a wastewater consultant to determine what’s feasible.

Jason Hall is the owner of Central Carolina Soil Consulting. As a licensed soil scientist, he provides on-site wastewater disposal insights to builders, developers, and homeowners across the Triangle. He said many homeowners don’t fully understand what goes into a septic system, but the system and its structure can determine whether you can support the additions you may want for your home.

Here are a few things you’ll want to understand about your septic system if you’re a homeowner.

It’s likely you already know a septic system removes wastewater from your home. But your septic system is also key to knowing how a home is listed in the real estate market and the kind of key features your home may have.

“Every home in Wake County, and in North Carolina for that matter, has to have a functioning septic system, hopefully in suitable soils that meet state, local, and county regulations,” Hall said. What people often don’t understand is everything that goes into that system. “Ninety percent of the public thinks their septic field is just the tank that’s sitting in the yard with the two riser lids. They don’t realize they have so much area that’s taken up with their leach field, and that’s where the soil does the treatment of the effluent before it gets absorbed in the ground.”

He explained that typically, the leach field is in a large, open area of your yard. “That’s normally in the backyard, and that’s right where you want to put your pool or patio and things like that. You have to redesign them while working within the regulations and making sure we’re following the rules we have to follow. And that’s while also trying to help the homeowner get what they want on their property.”

Hall also explained that a septic system is planned to support the number of bedrooms in a home. A home’s daily flow rate, which is set by the North Carolina Department of Environment and Natural Resources, is 120 gallons per day per bedroom. “You can imagine a three-bedroom house versus a six-bedroom house,” he said. “Obviously the septic field is twice as big just because of that daily flow rate.”

If you’re thinking about increasing the size of your home, including the addition of an accessory dwelling unit (ADU), your septic system will likely need an update.

“If you have a four-bedroom house and you want to add an ADU to have your mother or father live there, that’s another two-bedroom flow rate that you have to put on that lot,” Hall said. “If you had a four-bedroom system there to begin with, now you have to have enough space on the lot to fit a whole new two-bedroom system and a backup field on the lot.”

Hall added that the size of a lot can hinder this type of addition to a home. In 2020, when homeowners added swimming pools to their homes to have something to do while home during the COVID-19 pandemic, that demand increased his workload significantly.

“I think we had almost a 300 percent increase on the demand for looking at existing lots and trying to redesign septics,” he said. “The key is trying to redesign it where you meet the rules and regulations, you still have a functioning system, but you also allow the homeowner enough space to utilize their yard the way they want.”

Hall said there are new septic options that have helped ensure there’s enough space for the additions homeowners want to make. The first is a panel block system. Rather than losing between 35 to 40 percent of a lot’s yield, this technology saves on space without sacrificing septic quality. “We can shrink the footprint down,” Hall said, pointing out that this technology can save an extra 25 percent in area, which could accommodate a swimming pool.

“The other that came on about five years ago, is an engineered flow reduction. And, and basically there, if you work with a professional engineer (PE) licensed in the state, they can redirect that daily flow rate.” Hall said engineered flow reduction can reduce flow rate by 25 percent. “Basically, we go from 120 to 90 gallons per day per bedroom,” he added.

Hall also said builders can use low flow fixtures that help reduce that flow even more and meet green energy certifications, which are beneficial, too.

Hall said the term “suitable soil” refers to the soil depth within an area you have to work with. “We just want to make sure every lot has a ‘perk area,’” he said. “What we’re looking for is 30-plus inches of usable soil up here in the Piedmont. You don’t want water table rock, expansive clay, anything like that.”

Depending upon where you are in North Carolina, Hall said your septic system may need to be changed. For example, in Apex and Cary, Hall said, “You may not have 30 inches of usable soil. You may have 18 to 20, and you may have to use what’s called a drip system. There are different technologies you get toward the coast where you have really high water tables.”

He also said parts of Wake County don’t have good soil for septic systems installation. “The soil type basically has prevented three quarter acre or one acre lot developments over there because you don’t have the soils that will support it,” he said.

Hall explained that homeowners can find details about their septic fields in Wake County by visiting iMaps on the Wake County Geographic Information Services (GIS) website.

“If they type in their address, they’ll pull up their property information, and on the right-hand side of that website, there’s a little icon that says septic permit. If you click on that, it’ll take you to another page and you can download your existing septic permit.” Hall said homeowners can find where existing septic lines are on a property. For older homes, he said homeowners should call a consultant like him because the septic lines may not be in the Wake County database.

Having insight into what your system looks like may help you determine whether additions of a deck, swimming pool, or ADU is feasible or if it may cost too much to be worth it.

His advice is to reach out before making any plans. “Make sure they’ve had a licensed soil scientist look at the property or get a permit from the county they’re in to see what kind of system that will support.”

The Jim Allen Group provides access to information on this blog/website as a public service for educational purposes only. Although reasonable efforts have been made to ensure that all of the information made available is current, accurate, and complete…[read more]