Just like you, 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.


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, however, 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.   

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Generally, finer textured soils will require longer resting periods than sandy soils. You need approximately three 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. 

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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 in 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 GEO-flow HDPE Pipe-Leaching System from Advanced Drainage Systems promotes an oxygen-rich environment for increased biomat activity. It is comprised of a 10-inch-diameter, single-wall high-density polyethylene (HDPE) corrugated pipe surrounded in a polypropylene grid, both encased in geotextile fabric.
  • The Dirty Bird vent pipe filter from BS Design Corp. has been tested at the AIRVAC facility to serve as a concealment device for residential AIRVAC 4-inch vents, covering unsightly pipes protruding from an otherwise traditional landscape. It includes a matching birdbath basin that threads into the pedestal top.
  • The Spider Valve assembly from Clarus Environmental is designed for effluent distribution when regulations require pressure splitting or when a small lot requires lateral lines of unequal length. The valve is available in models ranging from two to 10 laterals and mounts in a 24-inch-diameter access riser.
  • The 108 Model decorative rock enclosure septic lid cover from DekoRRa Products is designed to fit over lids up to 25 inches diameter and over risers up to 4 inches in height. It has a realistic RealRock detailed design available in four colors, and includes plastic stakes for securing it to the ground.
  • The Wasteflow dripline irrigation system from Geoflow is placed directly into the soil, at the plant’s root zone, so effluent is released slowly and uniformly to be digested and absorbed safely. It can be used on difficult sites, including shallow soil profiles, steep slopes, limited setbacks or poor soils.
  • The GST Leaching System from Geomatrix Systems uses a removable form to accurately shape and construct leaching fingers along the sides of a central distribution channel. It’s constructed with 3.4-inch washed stone and is surrounded with ASTM C-33 sand.
  • Quick4 Plus Chambers from Infiltrator Systems provide unobstructed infiltration into soil in a variety of drainfield applications. They are available in standard, low-profile and high-capacity models, and have a Contour Swivel Connection permitting 10-degree turns, right and left.
  • Bioline polyethylene, low-volume dripline from Netafim is debris-resistant, continuous self-flushing and pressure compensating. It delivers a precise application rate into the soil over a broad pressure range, and has an impregnated antibacterial to prevent microbial slime buildup.
  • Septic system vents from Pagoda Vent Company passively ventilate on-site system components. They work in conjunction with the roof vent as air intakes, creating a draft through the system that clears gases and pressure within the system.
  • The Multi-Pipe (MPS) Rockless drainfield system from Plastic Tubing Industries uses corrugated pipes to replace voided areas within a gravel system. It provides a reduced footprint, lower profile, and increased transpiration and evapotranspiration area. All configurations are constructed with recycled materials.
  • Versatile distribution boxes from Polylok allow installers to choose the height of inlets and outlets. They come with a seal that accepts 2-, 3-, 4-inch and corrugated pipe (the 20-inch unit accepts 6-inch pipe). The 12-inch unit comes with stabilizing feet to anchor the box.
  • The passive Advanced Enviro-Septic system from Presby Environmental uses large-diameter pipe surrounded by fibers and fabrics to create an ecosystem that digests wastewater contaminants. Its Bio-Accelerator fabric speeds up the development of the biomat and allows for linear distribution.
  • Flow Divider/Directors from Quanics serve as stationary two-way splitter valves, containing a central weir, evenly splitting flow between fields. Their swivel action serves the dual purposes of evenly splitting or alternating flows between two lines. Alternating is ideal in situations where dosing and resting cycles are required.
  • The S-600 aerobic bacterial generator from SludgeHammer is certified by the International Association of Plumbing and Mechanical Officials Research and Testing Inc. and to NSF/ANSI Standard 40 as an advanced treatment system for residential wastewater.
  • Orifice shields from Sim/Tech Filter prevent drain media, such as drain stone, from blocking discharge holes to keep pressurized systems distributing effluent evenly. Their sturdy design keeps them firmly in place after snapping them on the laterals.
  • The Sweet Air Filter self-cleaning D-Vent filter from Tuf-Tite eliminates offensive odors from roof vents. It uses activated carbon to remove offensive odors, with heat from the sun automatically cleaning and refreshing the unit.

Want to learn more? Click here for complete product listings and manufacturer contact information.

About the Author

Jim Anderson is connected with the University of Minnesota onsite wastewater treatment education program, is an emeritus professor in the university’s Department of Soil Water and Climate, and education coordinator for the National Association of Wastewater Technicians.

Related: 5 Easy Fixes for Onsite Erosion Control

Send him questions about septic system maintenance and operation by email to kim.peterson@colepublishing.com.


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