How Much Does it Cost for a New Leach Field?

Also known as a drain field or soil absorption system, leach fields are an integral part of a septic system. If the leach field fails, replacing it can be costly. The cost of a new leach field depends on various factors. If your leach field needs replacement, get estimates from several contractors. You might save a few thousand dollars that way. Remember that septic system failure really means the leach field failed.

Failing Systems

Signs that a new leach field is necessary aren't hard to miss -- you will probably notice an odor and wet or permanently soggy areas in your current leach field. Pay attention to these warning signs and seek professional advice. You don't want the septic system to fail and have effluent back up into your house. Besides the personal inconvenience, failing leach fields can contaminate ground water, affecting drinking water supplies and potentially causing illness. If your field is near a water source, contaminants can cause algae growth in lakes and ponds.

How It Works

Anything going down drains and toilets heads into the septic tank. When wastewater and solids enter the tank, an initial baffle prevents wastewater from pouring in. This stops it from stirring up sludge in the tank. The outlet baffle prevents grease and scum from exiting the tank. Within the septic tank, the majority of solid waste settles in the bottom. Bacteria helps break this material down, and sludge forms. Wastewater continues on out to the leach field, usually through perforated pipe on top of a crushed or screened stone bed. Once in the leach field, the wastewater trickles down through the stone bed and into the soil.

In effect, the leach field acts as a giant filter. For best results, the soil in the leach field should be undisturbed and not compacted. Pathogens in the wastewater are absorbed by the soil, causing them to die off. Bacteria present in the soil also helps in the water cleansing process, along with common soil nutrients such as phosphorous and nitrogen. When wastewater can no longer be absorbed by the soil, the leach field fails.

Replacement Costs

Although costs vary according to the size of the leach field, soils and costs of local permits, expect to pay between $5,000 and $20,000 for leach field replacement. It is the most expensive component of the septic system. While areas with naturally sandy soil allow good percolation, or "percing" of the wasterwater downward, clay soils hold water.

The price of replacing your leach field depends heavily on soil type, as the field does not need to be as large for porous soil conditions as it does for less porous soils. If the section of your property containing the leach field is inaccessible and trees or fencing must be removed, that will also add to your costs. You also will need to factor in the cost of replacing sod in the area or planting new grass seed after the work is done.

Other Considerations

If you have to lay out money for a new leach field, take measures to ensure you don't need to replace it again for a long time. Do not plant trees or shrubs on or around the leach field; the roots can interfere with it. Don't park cars or store anything heavy on it, such as placing your boat on it when it's out of the water.

You'll also want to install water conservation devices in your house, such as low-flow toilets. Avoid taking long showers, doing more than one load of wash a day, or anything else that taxes the septic system. Have the septic pumped regularly, at least every two or three years depending on the number of users.

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