Septic tank systems
How they work
A septic tank is a large, underground, watertight container connected to the home’s sewer line. Its size is usually related to the number of bedrooms in the house.
Raw waste from the toilet, bathroom, kitchen and laundry flows into the tank, where solids separate from liquids. The solids fall to the bottom of the tank and light solids, such as soap and fat, float to the top and form a scum. This layer remains on top and gradually thickens until the tank is cleaned. Heavy solids on the bottom are gradually decomposed by bacteria. But some non-decomposed solids remain and build up into a sludge layer that must be pumped out (when the tank is cleaned).
Waste water from the outlet pipe flows into the drainfield, which purifies it before it returns to the natural groundwater system. There are many different types of drainfield, but essentially they are a series of long underground perforated pipes within layers of gravel and shingle. The liquid waste or effluent is distributed evenly into this. From here it percolates downward through the soil, which cleans it further. A small amount is taken up by the roots of plants, or evaporates.
Signs of trouble in a septic tank
In general, the life span of a septic tank system is about 20 or 30 years. The best way to avoid problems is to keep it well-maintained by regular cleaning (at least at three- to five-year intervals, depending on the size of the tank, frequency of use and number of users) and to leave the area over the drainfield undisturbed (with no heavy vehicles on it or trees planted nearby whose roots might enter the pipes).
If the tank isn’t cleaned regularly sludge builds up inside the tank and overflows into the house pipes and out into the drainfield, clogging it beyond repair. The following symptoms tell you that you’re facing a serious problem.
Slow-flushing toilets, and drains in the house flowing more slowly than usual.
Unpleasant odours round the home.
Sewage back-up in the drains or toilet — a black, foul-smelling liquid!
Liquid seeping along the surface of the ground near the tank system.
Lush green grass over the drainfield, even in dry weather. This might mean that liquid is welling upwards rather than going downwards as it ought to.
Build-up of weeds or algae in streams or lakes near your home, possibly caused by nutrient-rich water seeping into the groundwater. This could lead to possible health problems.
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