How A Septic Sand Filter Works

How A Septic Sand Filter Works

Sand filters are a good alternative to conventional septic tank/drain field systems in areas with shallow bedrock, poor soils or other restrictive site conditions. Sand filters treat wastewater using naturally occurring physical, biological and chemical processes that can be more effective than conventional systems. They also require less maintenance than centralized treatment systems.

The Septic Tank

The septic tank is a buried, water-tight container that receives all wastewater from your house. The wastes settle to the bottom of the tank where bacteria break down the heavier solids, forming sludge. The lighter solids, like fats and grease, rise to the top and form scum. Usually the tank is made of concrete, fiberglass or polyethylene. It has compartments and a T-shaped outlet. Inside the tank, bacteria live without oxygen and break down a lot of organic matter in your wastewater. They release gases, which are a sign that you need to call an expert to drain the septic tank. The effluent then leaves the septic tank through pipes that filter it as it enters the soil. This soil then purifies the liquid waste even more, preventing it from causing harmful impacts to your health or property.

The Filter Box

A septic sand filter is a type of sewage treatment system that filters wastewater through sand and gravel before it is absorbed into the soil. It is typically used in areas with high groundwater, shallow bedrock, poor soils or other site conditions that limit conventional drain field absorption. A septic sand filter can last 15 to 40 years, depending on the amount of water use and the loading rate at which it is operated. The septic sand filter needs to be cleaned regularly to prevent clogging.

The Drain Field

The drain field is a critical component of your septic system. The drainage field is composed of perforated pipes and gravel or sand. These materials help prevent waste runoff and keep critters away from your property. This reduces the risk of contaminating groundwater or fresh water sources. It also increases the life expectancy of your septic system. This is especially important if your site has poor soil or restrictive conditions such as high groundwater levels, shallow bedrock, or environmentally sensitive areas. A failing drain field is a serious concern that can lead to sewage spills, rotten odors in your yard, and even a complete septic tank failure (which wouldn’t be pretty).


If you have a septic sand filter, you’ll need to maintain it regularly to keep it working properly. This is important to prevent costly premature failure and to ensure that it is operating as designed and approved. Sand filters, single pass or recirculating, need regular cleaning of the surface layer to remove any accumulated solids that can cause clogging. How often this needs to be done depends on the type of sand used and the organic loading rates of wastewater entering the system. Generally, septic sand filters should be screened and graded as per accredited industry specifications and government approved guidelines to maximize treatment effectiveness and avoid expensive repairs later. A quality sand filter can last for years and provide effective septic treatment, if maintained correctly.