Landscaping Your Septic System

As septic systems become more complex and expensive, landscaping to maximize their life is an excellent investment. This article tells you how.

What is a Septic System? A septic system treats both your home’s sewage and gray water from showers, sinks etc. All waste water is piped to a septic tank from where it is distributed after depositing the solids in the tank to any of several secondary treatment areas including sand filters, mound systems and/or drainfield before entering the groundwater.

How Landscaping Affects Your System: The secondary stage of treatment relies on aerobic bacteria to treat the water before it enters the groundwater. Light, water, air, chemicals and heat all affect these bacteria to varying degrees. When landscaping it is important to consult an expert when altering these conditions.

Landscape Does and Don’ts:

  • Do request a copy of your septic “as-built” from the county Health Dept.
  • Do consult your septic designer or installer before changing areas over or within 25’ of your drainfield, sand filter or mound system.
  • Don’t burn over buried pipes: they melt!
  • Do keep irrigation to a minimum over marginal systems or sites with poor drainage. Divert run off away from your septic system.
  • Don’t bark, place plastic, or concrete over your secondary treatment area: it restricts air and has caused septic system failure through inducing anaerobic bacteria.
  • Don’t drive or place weights heavier than a riding lawn mower over your system (including livestock).
  • Do add septic “risers” to the lids of your septic tank if soil grade over the tank is deeper than 1’ and maintain easy access to the openings.
  • Do densely plant shallow rooted, evergreen plants over your secondary treatment area; it reduces water load on the system.
  • Don’t plant water seeking trees or shrubs close to the secondary treatment areas of your system: they will seek out the pipes.
  • Don’t add or remove soil over the secondary treatment area without consulting your installer.
  • Do plant water loving trees and shrubs at a safe distance around your or secondary treatment area (ultimate size of tree/shrub canopy should be horizontally more than 10 feet away). They will help lower the water table around the field, helpful on stressed systems.

A Few Landscape Ideas

Mound Systems: Small to medium sized evergreen shrubs can be planted attractively on the bottom half of the mound underplanted with groundcover. The mound can also be terraced or made into a gentle slope if the existing soil is left undisturbed and the soil required for this in brought in and added to it (being sure not to add any on the top of the mound).

Sand Filters: One of the nicest arbors I have seen was built to disguise a raised sand filter. Decks are another option, providing air flows freely through. Submerged sand filters can be treated like drainfields, only they are often more sensitive.

Drainfields: Lawn is an effective, common planting over drainfields. Others with the same type of root structure as lawn include drought tolerant evergreen groundcover such as thyme’s, Fragaria chiloensis and bulbs or perennials such as our native Sword Ferns and crocuses.