About one in four US homes have an individual onsite septic system. This means they are treating wastewater in the backyard, instead of sending it to the municipal wastewater treatment plant. Septic systems are an efficient, cost-effective method of treating wastewater.
There is no “new water” on our planet. Through the water cycle, water moves through rain, evaporation and other processes. Less than 3% of our planet’s water is freshwater, meaning it is a finite resource we need to protect. Every time we use water, we must clean it and return for the next use.
Individual septic systems treat wastewater, removing the bacteria and pathogens. It is then returned to the groundwater for the next use, which is often drinking water.
There are three components to every septic system: plumbing, a septic tank and the drainfield. They are designed to handle and treat the wastewater and accompanying solids.
Plumbing Collects Wastewater
Household plumbing is designed to carry clean water into the home and wastewater out. Exit plumbing collects all wastewater and sends it out to the septic tank. In addition to plumbing, adequate ventilation for gases is required. Homeowners in cold climates should ensure that these vent pipes do not freeze.
The purpose of the septic tank is to collect solids and prepare the liquid (effluent) for treatment and hold the solids until removed by a septic pumper. Baffles around the inlet pipe direct the water down so it enters under the water surface to limit agitation, and help keep solids from going back into the house in case of back-up. A baffle around the outlet pipe prevents solids from leaving the tank.
Waste separates into three layers. The scum layer includes light substances that float, such as hair and soapsuds. The bottom layer is sludge, the heavier wastes that sink. The liquid in the middle is effluent, which goes to the drainfield for treatment. The goal is to keep all solids in the tank, allowing only liquid into the drainfield.
There are manholes, or large openings on the lid of the tank. Pumping should be done through these manholes, and is required in some states. In cold climates, lifting the manholes to the surface with risers is recommended, and required in some states. This aids in winter pumping if necessary. Inspection pipes aid in monitoring the system and maintenance of some effluent filters.
Pumping or Inspecting the Septic Tank
Tanks need to be inspected and pumped on a regular basis to remove the accumulated layers of scum and sludge. The goal is to allow water enough time to separate out so no solids go to the drainfield. If the tank is full of solids, there is no room for separation to occur. Many states have requirements for pumping, check with local codes. As an example, Minnesota requires inspection or pumping every three years.
Trench and Mound Drainfields
Wastewater treatment happens in the drainfield. Soil bacteria destroy the harmful bacteria, viruses, other pathogens. Plus, an electromagnetic charge exists between pathogens and soil particles, so the pathogens are bound to the soil. Drainfields remove or reduce many of the nutrients in wastewater including nitrogen and phosphorus. Drainfields recycle some cleaned water and nutrients up to grass. The remainder percolates downward, replenishing the groundwater.
Research has shown that three feet of “good” soil are needed to provide this treatment. Good soil is dry and has the capacity to hold oxygen. The soil bacteria are aerobic – need oxygen to survive. Dry soil of any type (sand, clay, loam, silt) has the capacity to hold oxygen; it just cannot have been wet for extended periods of time.
If a property has the three feet of “good” soil, plus another two feet to accommodate the pipes and gravel and some topsoil, the site may have a trench if all other factors allow. If there is not enough space for a trench, this can be created by going up with clean washed sand. This is a mound system.
Decisions on what type of drainfield may be built are made by the septic designer on a number of factors including the soil type and condition, slope of the land, amount of space available, number of bedrooms, presence of a garbage disposal and other factors.
Septic System Maintenance and Management for Long Life
System maintenance is key is ensuring a system is working properly and remains efficient and cost effective. This is not difficult, but requires attention from the homeowner. There are many steps homeowners can take inside the home to reduce water and product use, protecting and extending the life of the septic system. Landscaping the drainfield or mound system will help the system function effectively. Check these resources for tips and ideas on maintenance and management of individual septic systems.