How Does Septic Sand Filtration Work and What Kind of Sand Should be Used?

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The addition of sand filtration to a conventional septic system is necessary if drain field absorption has previously failed or is limited due to high groundwater, shallow bedrock, poor soils, or other restrictive site conditions. Sand filtration is also a good choice for developments with reduced space.

That leads to two very important questions: how does septic sand filtration work and what kind of sand should be used?

How does Septic Sand Filtration Work?

Wastewater from a home first enters a septic tank, where heavy solids (known as sludge) settle-out, and uses oxygen to start the process of bacterial decomposition. This partially treated water (called effluent) then flows out of the septic tank by gravity, often to a pump chamber; pump chambers are only required if natural topography or flow are not ideal. The effluent then flows or is pumped-out under low pressure into a lined above- or below-ground Sand Filter Box through a network of perforated distribution pipes. These distribution pipes are enclosed in a gravel bed near the surface of the box so effluent can trickle downward. Contaminants will stick to the surface of filter sand grains and follow other sand filtration processes as the effluent slowly seeps through graded sand and gravel beds and is collected at the bottom of the box. Location-dependent, filtered wastewater is then pushed downward, or out into a drain field (also known as a leach field), by gravity or pump, through another network of perforated distribution pipes surrounded in gravel to trickle downward though the native soil and return to natural groundwater systems. Natural evaporation processes above the drain field will help the system function properly and extend the life of the entire septic system.

What Kind of Sand Should be Used in Septic Systems?

The lifespan of a septic system increases significantly with careful design, construction, installation and maintenance. Proper filtration sand quality and gradation are paramount during installation of a septic system to ensure longevity and avoid costly repairs. Septic Sand can be of various composition (i.e., silica or regular/brown sand), but should be screened and graded within accredited industry specifications and government approved guidelines to ensure effective sand filtration.

Aside from selecting accredited sand from a reputable dealer and having a professional Wastewater Installer, the following actions will increase the life of your septic system:

  1. Maintain aerated grass coverage, and never place heavy or impermeable items, on top of the septic system (especially the drain field) as it could restrict air supply or damage the system, preventing effective treatment.
  2. Check monitoring pipes regularly and inspect for odours or wet areas above the (optional) sand filter box and drain field. Seek professional help as soon as you suspect issues with your system!
  3. Conserve and maintain steady water flow and appropriate usage so not to overwhelm the system. Avoid using the system during prolonged power outages (>24 hours), as the pump will not be functioning to move wastewater (if your system is gravity fed only, it will not be affected by power outages).
  4. Keep harmful materials out of the system (such as bleach, grease, cooking oil, paper items, solvents, etc.), as they overwhelm and reduce efficacy by destroying bacterial and chemical balances.
  5. Have your septic tank professionally inspected and pumped at least once every two to three years.

Shaw Resources is an accredited supplier of high-quality Septic Sand and Gravel that is extracted and screened in Atlantic Canada as per government Disposal Systems Standards. Shaw Precast Solutions can also supply concrete septic tanks, pump chambers and well crocks. If you are thinking about installing, maintaining, or upgrading your residential or commercial septic system, contact your local filter media supplier and environmental regulator for standards and best practices specific to your region.