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How Close Can You Build to a Leach Field?

Home and Garage Construction

Are you planning a new garage, deck, or even a pool on your property? If so, you may be wondering how close you can build to your septic system, and specifically your leach field. In order to keep your septic system running properly, you should avoid building on or near your leach field. While it’s important to follow state and local building codes, plan to break ground at least 10 to 20 feet from where your leach field is buried.

What’s the Purpose of a Leach Field?

If you have a home with a septic system, all of the wastewater your home produces, through flushing the toilet, taking a shower, and even doing laundry, is collected in your septic tank. Bacteria in the tank break down the solid materials inside, and as the water level in the tank rises, it needs a place to go. Wastewater then makes its way into outlet pipes and eventually to the leach field.

The leach field is a series of perforated pipes buried in the yard, often in a bed of gravel. It allows the wastewater to gradually filter out through the gravel and into your yard. The leach field’s design keeps wastewater from pooling in one spot, and when it’s functioning properly, the ground should not hold any more water than the surrounding areas.

Can I Build Over a Leach Field?

The pipes used in your leach field are not designed for heavy impact. It’s recommended that the leach field should be an area that sees only light foot traffic. Driving or parking over the leach field could cause the pipes to burst, and a concrete foundation could create similar issues and make it much more challenging to repair a broken leach pipe, as well.

Not only could building over a leach field cause damage to the structure, it could also slow down the dispersing of the wastewater itself. That’s because oxygen is needed for evapotranspiration. The oxygen allows the microbes in the soil to continue to treat the wastewater as it flows out of the pipes. Building on top of a leach field would drastically reduce oxygen to the site, introducing potentially harmful bacteria to your yard.

Why Does it Matter Where I Build?

If building on top of the leach field is out of the question, you may be wondering if building your new garage, addition, deck, or patio right next to the leach field could be a possibility. Unfortunately, building too close to a leach field could also cause issues, not just for the leach field, but the structure itself.

First, construction near a leach field will likely bring heavy machinery to that area of your yard. If large trucks and construction equipment are driven over the area, the pipes could be damaged. In addition, if you are building near your leach field, there’s a chance you could be building on or near your septic tank. It’s important to keep that area free of obstruction so it can be pumped and repaired as needed.

If you’re considering a pool—either in-ground or above-ground—you may want to move it away from your leach field as well. Both could compact soil or bring extra water to the ground nearby. When the leach field is too saturated with pool water and wastewater, the ground could be compromised, and wastewater could inadvertently wind up in your swimming water. In the event you build a structure near your leach field and your leach field fails, you may also incur water damage and face health problems as wastewater seeps into the building.

How Far to Build From a Leach Field

Most states and localities have specific building codes that include how far you need to build from a leach field or septic tank. Distances could differ from one area to another based on factors like topography and soil composition. Before you break ground on any construction project, be sure to check with them first. The following are general building guidelines to give you an idea as you plan.

Most septic tanks need to be 5 to 10 feet from buildings. Leach fields, which are typically installed adjacent to the tank itself, should be 10 to 20 ft from any structure. This gives you room to safely maneuver construction equipment during the building process, and it should prevent wastewater from making its way into your structure as well.

Building Near a Leach Field

As you plan your building project, it makes sense that you’d want to best utilize the space on your property. While the large grassy area above your leach field may seem like the perfect place to build your garage, shed, or barn, building on or near your leach field is not recommended. Excess weight above the leach field could cause pipes to burst and water treatment to slow, and building too close to the area could result in damage to your structure as well. Check your state and local building codes before starting your project and give your septic system the space it needs to function properly now and for years to come.

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