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How Much Weight Can a Leach Field Safely Hold?

Leach Field Plumbed Ready for Bury

When homeowners consider their septic systems, they often focus on the septic tank itself. While maintaining the tank is critical to the system’s function, the leach field is just as essential. Whether you’ve just moved into a new property or you’ve been living there for years, it’s important to know where your leach field is located and how much weight that area of your property can safely hold.

What Happens if a Leach Field Bears Too Much Weight? 

The pipes in your leach field play a critical role in removing liquid waste from your septic tank and dispersing it into your yard. If too much weight is applied to the ground above the leach field, these pipes could crack or break. If you notice standing water in your yard or increased grass and plant growth, this could be a sign that your leach pipes have broken. You may also notice a foul odor. Over time, the breaks in your leach field could begin to affect your entire septic system. You may experience slower drainage rates or waste backing into your home.

In addition to causing pipes to break, putting too much weight on your leach field could also reduce its ability to disperse waste water properly. That’s because the process relies on oxygen for evapotranspiration. The oxygen helps the microbes in the soil to treat and breakdown the wastewater in the pipes. When this process is limited, harmful bacteria could be introduced to your yard.

Factors that Determine How Much Weight a Leach Field Can Hold 

Septic systems are not a one-size-fits-all solution, so each one is designed to meet the needs of the structure, property, and homeowner. Because of this, there isn’t a definitive weight limit that is the same for every leach field. To understand the actual weight your leach field can safely hold, consider these factors:

Depth of Leach Field

The deeper a leach field is built, the more weight it may be able to support.

Soil Type

Sandy soil may compact more easily, resulting in damage to the pipe system underneath when excessive weight is applied. Clay soils can withhold more weight before compacting and causing damage to the leach line underneath.

Groundwater Levels 

In areas where the groundwater levels are higher than average, the leach field and its components have less support to bear heavy weight.

Trench Width

Narrow trenches in the leach field have a harder time dispersing the load above it.

Age of the System

As the septic system and its parts age, pipes may become more brittle and more susceptible to breakage.


How Much Weight Can a Leach Field Hold? 

While you should consider all of the factors above, many professionals believe that the maximum weight for a leach field is around 10,000 pounds. Still, it’s important to be cautious of what you choose to do over your leach field to ensure it’s working properly.

Is it Okay to….

As you understand the importance of maintaining your leach field, you may also be wondering how you can utilize the area above it. Here’s some helpful tips to consider.

…Walk on my Leach Field?

Absolutely! As long as you do not detect standing water or sinking ground above your leach field, it is definitely safe to walk on top of it.

…Landscape on my Leach Field?

It depends. Laying sod or using grass seed can actually be helpful in maintaining the integrity of your leach field by keeping the soil in place. Trees and plants with long root systems, however, should be avoided, as the roots could damage the pipes. In addition, you may damage pipes while digging.

…Build on my Drain Field?

This is not recommended. Most state and local building codes prohibit homeowners from building permanent structures over existing leach fields, but even if your locality does not have this provision, it should still be avoided. Not only could the weight of your concrete slab damage the leach field, the weight of the construction vehicles could do the same.

Once your leach pipes are broken, it will also be much more challenging to repair under a permanent structure. Consider building your addition, patio, garage, or outbuilding at least 10 feet away from the area of your leach field and septic tank.

…Park on my Leach Field?

No. Focused pressure for long periods of time could cause leach pipes to crack or break, even if the vehicle’s weight does not exceed 10,000 pounds. Parking on top of leach fields should be avoided. 

…Drive on my Leach Field?

Use extreme discretion. Driving a smaller vehicle over your leach field once or twice may not cause damage to your leach lines, but it could damage the ground above, which could make your leach pipes more susceptible to damage in the future. Driving large vehicles over your leach field should always be avoided.

Avoiding Excess Weight on Your Leach Field

While many professionals believe that a leach field could bear about 10,000 pounds of weight for a short period of time, it’s often not worth the risk. While you can safely walk on your leach field, parking, driving, and building on the area above should be avoided. You may also want to take caution when considering how to landscape the property around your leach field.

To help maintain your leach field’s functionality, consider incorporating a bacteria-based product like BioOne into your routine maintenance. Once bacteria is added to your septic tank, it will help to break down the fats, oils, and greases inside, minimizing the likelihood of leach field clogs in the future.

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