Drain Fields – The Guide

What is a Drain Field:

Septic Drain Fields are used to remove impurities and any contaminants from the liquid that leaves the septic tank.  Drain Fields are often called Leach Fields, Weeping Beds or Leach Drains.  Drain Fields can come in a variety of designs depending on soil and property specifics.  A complete septic system is the septic tank, the drain field and any associated piping.

construction of a drain field

This typical drain field setup shows how perforated tubing in rows allows liquid waste to filter into the surrounding soil.


What is a Sand Mound:

Sand Mound or Mound System is an engineered drain field in locations where the soil has conditions that may be problematic.  Extremely Permeable or Impermeable Soils, High Water Tables and Porous bedrock can create conditions where normal drain fields will not work effectively.  The Mound System is designed to offset those concerns.

The Reasons for Drain Field Failure:

There are two reasons that a drain field can fail.  Hydraulic Overload and Biological Overload are the two reasons.  Hydraulic overload occurs when too much water is sent to an under designed system. Capacity is often determined by the number of bedrooms for a house.  This is not always accurate which is why as older homes are renovated or a hot tub is added, the amount of wastewater becomes too much for the system to handle.

Biological Overload when too much organic matter is in the effluent leaving the septic tank.  A drop in bacteria counts in septic tanks or excessive solid build up in the tank can lead to particles making their way into the drain field and developing Bio Mat, which leads to drain field failure.

Drain Field Maintenance:

Like all sewage systems septic systems need regular maintenance.  Drain Field maintenance is not any different from the septic tank maintenance.  Essentially, by taking good care of the bacteria levels within the septic tank and observing regular Septic tank pump out schedules you are taking the necessary steps to maintain your drain field.  If proper septic tank maintenance was overlooked and the drain field is failing, you need to seek out septic shock treatments for the system, or consider replacing the drain field.

Drain Field Rehabilitation:

There is much debate on the proper steps for drain field rehabilitation.  Contractors will usually recommend replacing the drain field with a new system in a new area of the property.  Other developments will attempt temporary relief until they can connect with a sewer system.  There are septic shock treatments designed to digest the biological overload or Bio Mat which can restore your septic systems drainage.  The process can take roughly a month, however the cost is a fraction of replacing the system.

Environmental Concerns:

A septic system that is maintained properly poses no significant environmental risks or concerns.  However when septic tanks are not properly maintained, the risk of groundwater pollution and surface water pollution can become a concern.