Resting a System to Restore Soil Infiltration

Onsite systems sometimes need some R&R. See how periodic resting can help restore soil infiltration, and learn what factors to consider when resting a system.

Resting a System to Restore Soil Infiltration
Most regulators require an entire soil treatment area to rest the system. Where the soil treatment area in question is viable, you can periodically switch between two full-sized systems.

Many researchers and onsite professionals have long recognized the benefits of periodically resting all or parts of a drainfield to restore soil infiltration. Intermittent resting lets bacteria mineralize the organic matter to unclog soil and ultimately restore infiltration. However, there are many factors to consider when resting a system. 

The main problem with resting is creating a long enough time period necessary for beneficial resting that generates long-term improvement. Depending on homeowners’ water use, pumping the septic tank followed by two to three days of resting usually won’t restore soil infiltration. Within a few days to a week, you can expect the system to be right back where it started. 

Another factor is determining how long the system needs to rest. The first step is to evaluate soil type and the biomat thickness and resistance.   

Generally, finer textured soils will require longer resting periods than sandy soils. You need approximately 3 feet of unsaturated soil below the infiltrative surface for soils to drain properly after effluent applications cease. For soils with periodic high water tables and particularly finer textured soils, the soils may not drain fast enough to promote biomat breakdown, even if applications are stopped for an extended period. 

Some onsite professionals used to install an additional set of trenches and route all of the effluent to the new area for at least a year on lots with suitable soil and enough land. This method requires additional valves to switch back and forth between parts of the system. When I first started in the industry, we used this strategy frequently rather than installing a completely new system. 

Today, most regulators require an entire soil treatment area to rest the system. Where the soil treatment area in question is viable, you can periodically switch between two full-sized systems. While I don’t disagree with this approach, if you are dealing with a small lot with limited quality soil, you can sometimes work with the local regulator to get approval to install a partial system with the built-in resting to provide necessary resting time. 

Hint: Be sure to investigate water usage and effluent quality before resting a system to restore soil infiltration. Check homeowners’ water-use patterns and evaluate whether there is sufficient septic tank capacity to provide the necessary effluent quality into the soil treatment area. Resting might not be necessary if homeowners can reduce their waters usage or if you find that a larger system is the only option. 

If industry professionals are serious about system management, shut-off and resting components should be built right into the design and original installation. Coupled with a regular maintenance program, this will ensure system longevity. 

From pipe vent filters and leaching systems to decorative septic lid covers, we've gathered these components for all your drainfield media and design needs: 

  • The Septic Stack system from Advanced Drainage Systems is designed to allow for exceptional soil contact without use of gravel, functioning as a trickle filter to disperse effluent into the voids in and around specially banded ADS pipe.
  • The WW4 effluent filter from Clarus Environmental is mounted in the outflow of the septic tank to provide protection from solids moving out of the tank and into the dispersal area.
  • The GSF, or Geotextile Sand Filter, advanced wastewater treatment and dispersal system from Eljen is designed to provide treatment and dispersal in the same footprint while keeping installations easy and maintenance minimal.
  • The GST Leaching System from Geomatrix Systems is an adaptation of the stone leaching trench.
  • Pleated filter units from Sim/Tech Filter provide gravity effluent filtration in septic tanks and turbine pump filtration in pump tanks.
  • Tank risers from TUF-TITE have internal supports or ledges to reinforce internal plastic safety lids.
  • Septic vents from Pagoda Vent are designed to help enhance system function with landscape appeal and homeowner approval while providing the necessary ventilation to the drainfield. 
  • The Poly-Air activated carbon roof vent from Polylok can help remove offensive odors, such as hydrogen sulfide, as they come out of the roof vent.
  • The solar-powered Super Wolverine vent filter from Simple Solutions Distributing is designed to eliminate odorous airflows up to 10 cfm, and the solar fan vents the tank, reducing accumulation of sewer gas. 
  • The Dirty Bird provides an alternative to the standard septic vent required by many municipalities for new residential and commercial construction.

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