Septic tanks are essential structures, but they can be an inconvenience if you want to build over them. So, can you put a concrete patio over a septic tank, or is that unsafe?
In most counties, building right over a septic tank is a code violation, so the answer is no. However, if you want to build your concrete patio near a septic tank, you should be able to if you stick with the required clearance.
So why is building over a septic tank such a bad idea? Read on to find out!
Why Can’t You Put a Concrete Patio Over a Septic Tank?
Although they might seem like inert structures you can ignore in your backyard, septic tanks aren’t passive and require more attention than you might think. That’s why area building codes consider it a code violation to build over a septic tank.
These rules aren’t arbitrarily made to make your life harder, though. Here are the reasons why you can’t build over a septic tank:
1 – Loss of Access to the Tank
Residential septic tanks of any kind require regular pumping and servicing every 3 to 5 years, depending on multiple factors. These factors include the number of residents in the house, the type of plumbing configuration, and the capacity of the septic tank.
Most modern tanks can be accessed through two openings at the top. The access points should always be visible and within reach to make the pumping process streamlined and rapid.
If you build a concrete patio over the septic tank, you’re blocking the tank’s access points. Should any problem arise within the tank that requires immediate pumping, you have to tear down the patio to reach it.
2 – Compromising the Tank’s Structural Integrity
By definition, a tank is a hollow structure that has a roof. No matter how sturdy the construction is, there’s only so much pressure a fiberglass septic tank can endure.
Pouring a concrete slab over the tank’s roof could very well compress the tank beyond its breaking point. That might make the tank shift and/or crack, causing irreparable damage and leakage.
Now, this is more of a problem if you plan on building a driveway over the septic tank, but even with a concrete patio, the issue still stands. When the time comes to get the tank pumped and cleaned, the patio might get damaged by professional equipment.
3 – Impairing the Tank’s Function
Septic tanks work through a process called evapotranspiration. In simpler terms, it means the liquid portion of the waste is transported through drain pipes with holes so the water escapes and evaporates, while the solid portion remains in the tank where bacteria turn it into sludge.
This process requires ample aeration so that oxygen can aid bacterial growth. If the septic tank and its drain field are obstructed by a structure, this can suffocate the tank.
Can You Put a Concrete Patio Near a Septic Tank?
Since building right over a septic tank isn’t an option, how near can you place a concrete patio to a septic tank?
Well, the answer depends on your area’s building code, but in most counties, you can build any structure 5 feet away from a septic tank, drain field, or drain pipes. As for swimming pools and water wells, the distance can vary from 50 to 150 feet.
The idea here is to leave enough clearance to allow for easy access to the tank, and at the same time, not impair water evaporation and oxygen penetration into the soil.
Another option you have is to build the concrete patio at an elevation of at least 3 feet. Using a platform to build upon allows for air circulation and moisture escape. Just keep in mind that the posts should be at least 5 feet away from the septic tank’s access points.
Can you put a concrete patio over a septic tank?
While the answer “no” sounds discouraging, it’s all for a good reason. Building over a septic tank creates more problems than it solves. The concrete patio ends up barring access to the tank, threatening its structural integrity, and impairing its function.
That’s why you should stick with your area’s building code to determine how far to build your concrete patio so you wouldn’t have to tear it down.
Ben has a bachelor’s degree in construction engineering. When not constructing or remodeling X-Ray Rooms, Cardiovascular Labs, and Pharmacies, you can find him at home with wife and two daughters. Outside of family, He loves grilling and barbequing on his Big Green Egg and Blackstone Griddle, as well as working on projects around the house.
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