The Drainfield

How It Works

The drainfield is a network of perforated pipes (or “laterals”) laid in gravel-filled trenches or beds. After solids settle in the septic tank, the liquid wastewater (or effluent) is discharged, either by gravity or pressure, to an absorption field, also known as a drainfield or leachfield. NOTE: In most gravity systems the wastewater first flows into a distribution box (d-box) or tee, which then disburses the effluent equally among the trenches in the drainfield, which is where the final treatment takes place.

Effluent trickles out of the pipes, through the gravel layer, and into the soil where further treatment occurs. The soil filters the wastewater as it passes (or “percolates) through the pore spaces and the soil microbes treat it before it eventually enters the groundwater. These processes work best where the soil is somewhat dry, permeable, and contains plenty of oxygen for several feet below the drainfield.

The drainfield is generally located in a stretch of lawn in the back or side yard of a property. The size and type of drainfield depends on the estimated daily wastewater flow and local soil conditions.

The Soil

The soil below the drainfield provides the final treatment and disposal of the septic tank effluent. After the wastewater has passed into the soil, organisms in the soil treat the effluent before it percolates downward and outward, eventually entering ground or surface water. The type of soil also impacts the effectiveness of the drainfield; for instance, clay soils may be too tight to allow much wastewater to pass through and gravelly soil may be too coarse to provide much treatment.

Replacement (Reserve) Area

Every new home or building served by a septic system is required to have a designated replacement or reserve area. This is a designated area suitable for a new drainfield and must be treated in the same manner as your existing drainfield. (A reserve area should have been designated as part of the permit process for any sewage system installed since 1980.)

Once a septic system has failed, it is too late to solve the problem by pumping your tank. A new drainfield will have to be installed at a different location. This is why it is important to know where the replacement area is located and how to protect it (see “Drainfield Do’s and Don’ts” for replacement area care).

Septic System Do’s & Don’ts

Septic System Do’s

1. Inspect your septic tank annually - Septic Tanks should be pumped every three to five years. An inspection by you or Lilly’s Technician may show that you need to pump more or less often. Regular pumping ensures that solids will not flow from the septic tank into the drainfield. Solids  destroy the drainfield, and once a drainfield has failed, pumping will not bring it back to life.

2. Use less water - Reducing the amount of wastewater entering your Septic System may increase its life span, as excessive water is a major cause of system failure. Too much water from laundry, dishwasher, toilets, baths, and showers may not allow enough time for sludge and scum to separate, causing solids to pass out of the tank and into the drainfield, ultimately clogging the pipes. To reduce household water use:

• Limit the use of large water guzzling appliances, such as dishwashers and washing machines.
• Use water-saving bathroom and kitchen fixtures (such as faucets, showerheads, and toilets).
• Spread laundry over the entire week and avoid all loads on one day.
• Fix all faucet and toilet leaks promptly.

3. Direct water from downspouts and roofs away from the drainfield - Additional water from these sources may prevent your drainfield from working properly.

4. Keep cars and trucks off the septic tank and drainfield areas -  This prevents pipes from breaking and soil from becoming compacted. Compacted soils can’t absorb water from the drainfield.

5. Use phosphate-free detergent - Phosphorus is harmful to the environment, as it can deplete oxygen which is vital to fish and other aquatic organisms. The use of phosphate-free detergents, also helps prevent algae problems in nearby lakes and streams.

6. Use non clay based Liquid Laundry/Dishwasher Detergent - Liquid Detergents do not crystalize like powders do and create blockages in the baffles.  Clay based detergents tend to create excess sludge in a Septic Tank.

7. Install risers for easier access. Risers from the tank lids to the soil surface to make maintenance easier and avoid digging charges when you pump your Septic Tank.

For more information about your Septic System and to schedule service contact us at:

Septic System Don’ts

1. Limit garbage disposal use - A garbage disposal adds solids and grease to your system, which could lead to drainfield failure.

2. Don’t use septic tank additives or “miracle” system cleaners - Some of these chemicals can actually harm your on-site sewage system by allowing solids to flow into and clog the drainfield. Some of these additives claim you never have to pump your Tank if you use them.  The reality is that you may not have to pump your Tank regularly but you’ll have to replace you Drainfield instead.  The chemicals can also contaminate ground and surface water. 

3. Don’t dispose of water from hot tubs into the on-site sewage system - Large volumes of water are harmful to the system, and the chlorine can destroy important bacteria in the system. Drain hot tubs onto the ground, away from the drainfield and not into a storm drain.

4. Don’t flush solid wastes into the septic system - These include diapers, cigarette butts, coffee grounds, tampons, condoms and grease.

5. Don’t put strong chemicals, such as cleaning products, down the drain - Household chemicals, such as drain cleaners, paint thinners and floor cleaners, can destroy important bacteria in your septic tank and contaminate ground and surface water.

6. Don’t construct patios, carports or use landscaping plastic over the drainfield - Grass is the best cover for your septic tank and drainfield. Soil compaction and paving prevents oxygen from getting into the soil. This oxygen is needed by bacteria to break down and treat sewage.

 Septic System Do’s and Don’ts by Lilly’s Septic Service

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