The Different Types of Septic Systems
It’s important to know what type of septic system is installed in your home, which impacts how your maintenance and inspections are performed.
There are four main types of septic systems:
- Mounds and Fields – These are two separate types of septic systems but they essentially operate the same, with the main difference being in appearance and in the construction of the final treatment area. Mounds sit slightly above the surface where the final treatment occurs while fields are flat and lay at or below the surface. The types are referred to as a ‘conventional system’ containing a two-chamber septic tank. Solids settle in the first chamber and a clarified liquid passes to the second chamber where it’s sent to the final treatment area in the soil by a pump or by gravity. Field systems typically last 20-25 years while mounds are between 15-20 years before repair might be required. Over 80% of failing fields and mounds can be qualified for repair without replacement.
- Sand Filters – Sand filters are a form of secondary/advanced treatment to produce higher quality effluent to be discharged to a smaller field, smaller mound, or an at-grade for final treatment. This type of system tends to have an 8-10 year lifespan before it gets clogged with organics and biomat. Nearly 100% of failing sand filters are repairable without replacement.
- At-Grades – The newest and most common type of septic system construction, At-grades are constructed on the surface of the property, covered with wood chips for a layer of insulation, and require secondary/advanced treatment upstream at the septic tank to create high-quality effluent. At-Grades typically generates the smallest carbon footprint and should last indefinitely with proper care and maintenance.
- Open Discharge – The oldest type of septic system discharge construction. Open discharges are constructed to directly expel untreated effluent on the surface of the property. Open discharges are highly regulated to be exclusive to large properties, typically over 20 acres, with very specific minimum distance restrictions and standards that must be followed.