Septic Systems


	What is a Septic System

	A septic tank is, a vessel into which sewage waste is directed from an associated premises, and wherein the solids-material is retained and digested by anaerobic bacteria, with the resulting supernatant/liquid, known as "sullage", flowing out via the discharge pipe for disposal or further treatment. The vessel/tank may be constructed of concrete, plastic or fibreglass and can vary in size or holding capacity. Older septic tanks used in the domestic site are usually 1850 litres or 2400 litres, whilst most modern installations use 2850 litre or 3300 litre tanks.




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	Commercial premises may use a domestic size tank or lager capacity tanks, dependant on the numbers of staff or public whom may use the facilities there. A septic tank may also be referred to as a "solids tank" or, the "primary tank" in a septic system involving more than one tank


	Why Pump out a Septic System?

	Here we see that after a period of use (3-5years) the black sludge layer has increased in volume in the bottom of the tank and the solids raft on the surface has also thickened. Now as more waste enters the tank there is nowhere for it to rise to the surface, or sink to the bottom, settle and be worked on by the residing anaerobic bacteria and be broken down. When the septic tank reaches this stage it is no longer operating correctly and doing the job it is supposed to do.This results in the supernatant flowing from the outlet pipe of the tank,



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	no longer being reasonably clear, but carrying in it the non-retained solids. These solids will now either flow down to contaminate the absorption trench, or flow into the secondary tank of a septic system. As these solids build up in the trench or secondary tank, they can be very damaging and prevent these parts of the septic system from operating efficiently.


		Q. How often should your septic tank be pumped out? A. A standard domestic tank should be pumped out every 3-4 years.This may vary with the number of persons using the system. Q. How can you tell if your septic tank needs pumping out A. You can check the level of your tank through the inspection hole located on the lid of the tank. Indications of an overloaded system may be a slowing of waste removal in the bowl after flushing, a gurgling sound from the plumbing upon emptying of utilities, or a sewage odour coming from the floor waste drains. Q. What information will you need when booking a pump-out? A. What type of system you have (e.g. single or dual tank systems); if it is a treatment system (e.g. Biocycle, Envirocycle etc) how many tanks are to be pumped out; and accessibility to tank (how close we can get a truck to the tank & how level the ground is). Q. How much notice will you need to give? A. Preferably 2-3 days notice. Q. What areas do we service? A. Sydney Metropolitan and surrounding suburbs.

	What is an Absorption Trench?

An absorption trench operates normally in the following manner. As sullage, or grey-water, flows from the septic tank via the outlet pipe into the trench, the water level rises and passes through pores in the plastic trench-liner into the rubble outside. Now the water is in the rubble it is drawn up through the rubble by capillary action towards the ground surface. Whilst passing through the rubble and then sand and soil layers the nutrients or contaminants are worked on by naturally occurring bacteria further purifying the water. Finally as the water nears the ground surface it is drawn up via evaporation or transpiration from the grass covering by the sun. The UV-rays of the sun further acting as a purifying action on the wastewater.

When a septic tank is not cleaned out in the appropriate time and the solids matter is carried via the sullage into the trench, the solids form a layer on the sides of the trench-liner blocking the pores in the liner preventing the passage of the water through to the rubble layer. And if let go too long the solids may even be forced through the pores into the rubble, filling it with a thick gluey/greasy sludge that prevents the trench from operating




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properly and instead of the trench drying out by the usual process it tends to retain the water, not drying out completely. This results in a constantly wet or boggy area in the region of the absorption trench. The efficiency of an absorption trench can also be affected by heavy or prolonged periods of rain.


	Locating an Absorption Trench

An absorption trench requires sunlight to operate at its most efficient so therefore it should be located in an area that receives the most sunlight.If the ground is flat there are no further considerations, however if the ground slopes in a particular direction it is important to construct the trench so that it runs at right angles to the direction of the slope. That is it must run across the slope and not with it.




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