septic tanks
How does it work?
A septic tank is a system, typically installed underground, which collects sewage, allowing the waste to decompose before disposing it through the means of a soakaway. A septic tank will treat wastewater from premises which are not connected to the mains drainage system. A septic tank works like a simple sewage treatment plant, except that it is a completely passive system powered entirely by gravity.
The process begins with waste-water flowing in through one end of the tank Waste material can settle in the tank and is digested by natural bacteria which must be allowed to breed within the tank. As new water enters the tank, it displaces the water that's already there. This treated effluent drains from the tank’s outlet pipe, normally to a soakaway field drainage system.
There are three layers to the waste that is collected within the tank:
- Top: The Scum Layer – Waste that can float will inhabit this layer.
- Middle: The Water Layer - This water contains bacteria and chemicals like nitrogen and phosphorous that act as fertilizers, but it is largely free of solids.
- Bottom: The Sludge Layer – Anything that is heavier than water will sink here.
To keep the septic tank running efficiently, it is recommended that the sludge built up within the septic tank must be cleared out every 12 months.