Guide to Properly Installing Gravel Over a Leach Field

Conroy Baltimore
Written by Conroy Baltimore
Updated March 24, 2022
Front of a home and yard in California
Photo: Trinette Reed / Stocksy / Adobe Stock


  • Granite gravel is the best option for a leach field bed.

  • The gravel amount depends on soil composition and septic system size.

  • Leach field depth should be around 3 to 4 feet, depending on the size of your space. 

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A drain field—aka leach field— is integral to your home’s waste removal process. The sloped pipes connected to your septic system keep wastewater away from your home and get deposited into gravel or sand to prevent runoff. 

The only drawback? It sticks out like a sore thumb in the yard. But you’ll be happy to know that you can spruce up a leach field with gravel, and we’ll explain why it’s the best option.

Why Homeowners Use Gravel for Septic Systems and Leach Fields

Pros and homeowners alike use gravel for septic systems and leach fields because of its ability to withstand heavy amounts of weight without getting crushed. This helps support your septic system and provides additional help during times of heavy flow.

Homeowners also choose gravel because of its smooth finish, look, and drainage ability. Without proper drainage, you might have wastewater all over your yard—and that isn’t fun for anyone!

How Much Gravel Can Go Over a Leach Field?

The amount of gravel that can go over a leach field will depend on the size of your septic system and the soil’s composition. Let’s say you have a typical two-bedroom house; you’ll need at least 200 square feet of gravel if the soil is coarse and sandy. 

However, if you’re installing gravel in clay or loam-based soil, you’ll need a bed of at least 1,200 square feet. All beds will have a thickness of at least 1 foot, while the surface area measures the bed’s size. 

You don’t want to put too much gravel over your leach field because it can cause improper waste drainage and damage your septic system. Then you’ll be looking at $3,000 to $10,000, which is the cost to install a new septic system.

How Deep Should a Leach Field Be?

 A backyard with gravel
Photo: GCShutter / E+ / Getty Images

Generally, you’ll want to have a leach field that is at least 3 or 4 feet in depth. It helps accommodate the gravel surrounding the pipes—12 inches underneath and 2 inches on top. Then you’ll backfill the area with soil to even everything out.

But they don’t always need to be that deep. Some leach fields can have drain pipes six inches below the surface. Underground obstacles like a slab of bedrock beneath the soil create an impermeable layer making it more difficult for your septic system to remove wastewater properly. 

In this situation, keep the drain field at least 1 to 2 feet above the underground obstacle. You can do this by making the area broader and longer.

The Type of Gravel to Use for a Leach Field

Like many stone types, gravel comes in various sizes and shapes, so knowing which to use is important. Using smaller rocks causes your septic tank to overflow with water, leading to a backup in your house (Ew). 

But larger pieces of gravel will cause water to flood the soil around your tank and enter your yard (Also ew). For the best results, use rock that’s one and a half inches in diameter.

As for the material, you’ll need to be selective. Not all gravel comes from the same crushed rock, so they won’t serve well in some projects. For example, a softer stone, like shale, is more beneficial for decorative purposes than your septic tank bed. 

Remember, the gravel bed has to be sturdy enough to hold the weight of a septic system full of waste. If not, we know what happens. Granite gravel would be a better stone choice because it’s wallet-friendly and durable.

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