Often dominant in rural areas and suburban communities without extensive sewer networks, a septic system consists of a subterranean tank and a soil absorption field. The tank is where household sewage–from kitchen drains, bathrooms and laundry areas, e.g.–is treated. After the oil, grease and solids separate from the effluent (i.e. wastewater), the water is then gradually expelled through perforated piped into the soil. Although this design is common among all kinds of tanks, size, efficiency, and performance vary widely. You will benefit from understanding the different types of septic tanks before you select one for installation.
Before determining what kind of tank is optimal, decide what sort of septic system best fits your property and needs. There are several system designs:
- Gravity system — using the natural force of gravity to move effluent into the leaching field.
- Pressure distribution — utilizing a pump to more uniformly distribute the wastewater.
- Aerobic treatment unit — applying oxygen to decompose the solids; considered “greener” than gravity and pressure systems.
- Mound system — where drain field sits above ground level.
- Sand filter system — using sand to filter the effluent of organic matter.
Eachare more or less accommodating for certain kinds of tanks.
Concrete septic tanks are famous for durability and longevity. In fact, they will last for multiple decades unlessthey go uninspected for long periods. In some cases, cracks can develop: out of such can leak wastewater, which could also allow groundwater in.Both runoff and blockage are possible without regular evaluation. Concrete tanks often accompany gravity and pressure distribution systems.
While certainly less expensive than a concrete tank, the steel tank has issues to be aware of. It is, of course, prone to rust, the cover rusting faster than the tank itself. Some owners have unwittingly replaced the covers without realizing the tank was also oxidizing. On the outside, steel tanks last for about 20 to 25 years before needing replacement.
Plastic and Fiberglass Tanks
Tanks made from plastic and fiberglass avoid the cracks and corrosion of the types listed above. They are frequently placed closer to the surface when soil is not abundant, as with mound and sand systems. All the same, they have their negatives. They will leak if and when the plug becomes knocked loose (the light-weight tanks are sometimes jolted easily). It is imperative, therefore, that homeowners frequently monitor the hydrostatic pressure gauge to make sure the effluent levels are not too low or high.
The centerpiece of aerobic septic systems, aerobic tanks require electricity to draw oxygen into them. To be frank, they are expensive and need more maintenance. On the bright side, aerobic tanks save valuable land by decreasing the amount of drainage field. The oxygen-fueled breakdown of solids keeps effluent levels low. The soil-friendly aspects are attractive to environmentally-conscious homeowners.
So, septic tanks are a chore, but a necessary one where sewer lines are absent. Consulting a surveyor or environmental engineer is a good first step when installing or replacing a septic tank. A professional will help you analyze your options from a cost-benefit perspective. Given the expense, this is wise.