Older houses may have one, two or three septic tanks, depending on the number of bathrooms, a grease trap (usually outside the kitchen window) and a sullage or ‘grey water’ tank.
All the waste from the toilets will go firstly into the septic tank and then to the absorption trenches. Kitchen sink and laundry drains will go firstly to the grease trap and then to the sullage tank. From there the waste or ‘grey’ water will be pumped out onto your garden or paddock.
Newer properties are more likely to have a much larger ‘all-in-one’ liquid waste treatment system. These come in many different forms and are often known by their brand names such as Bio-Cycle, Sep-Tech, Aqua Nova, Aussie Clean, Super-Treat etc. These systems collect all the liquid waste from the house and pass it through a four stage aerated filtration process to break down the solids as much as possible and then allow the remaining grey water to soak away via absorption trenches, sand beds or aerobic treatment systems.