- Last updated:
- 12 Oct 2020
On-site sewerage systems store, treat and dispose of household wastewater.
Septic systems consist of a watertight tank that retains any organic matter and solids for twenty four hours, so that it can be broken down by bacteria into a sludge layer that will sink to the bottom and a scum layer that will float to the top. Out of the middle of the tank an effluent flows out to a trench area. This trench is usually full of gravel and some pipes.
Septic systems release effluent into the soil at a depth where it won't come into contact with people. Septic systems are not suitable for highly sensitive areas as they may contaminate surface and ground water.
I am going to demonstrate some of the checks you can perform at home to monitor the health of your system.
Annual checks of the sludge and scum layer and filter are simple to complete. Septic tanks contain pathogenic organisms, bacteria and viruses. It is important that whenever you work on a septic tank you have eye protection, gloves and long sleeves and trousers.
To access the septic tank you need to remove the access covers, for that you will need a cordless drill or driver, and some screwdrivers. It is quite simple to remove the inlet cover, put the two screwdrivers in the slots, put a screwdriver in between and twist. We can do exactly the same with the outlet cover. To remove the main access cover a cordless drill is useful.
Once you have removed the covers, check the main chamber to see the condition of the scum layer. We are looking for it to have a nice crust and to be firm on top.
We will have a look at the cleaning the filter now, because cleaning the filter will allow your septic system to work at maximum efficiency for much longer without blocking up your absorption trenches. Remove the filter and wash it into the tank, once the filter is washed replace it and we're done.
To check the sludge and scum levels within your tank, you will need a sludge judge or you can use a stick wrapped in a white cotton cloth that will display the layers within the tank.
Using the sludge judge, lower it carefully down the inlet or the outlet depending on which one you are checking. Lower it as slowly as you can so you do not disturb the layers of sludge and scum. That is what we are checking for. We are checking to see how much sludge is contained in the bottom of the tank to see whether the septic tank needs to be pumped out. In this case we have got about 250mm of sludge contained within the tank.
We are also checking the scum layer, but because I have pushed the sludge judge down through the baffle I have not picked up the zone of the scum, but I can see from looking in the tank at the water level it is about 250mm as well.
Another important point to look for is the particulate display within the tube or attached to the white cloth. The more particulate you can see, the dirtier the effluent zone is and the closer the septic tank is to needing to be pumped out. This material is easily carried over to your absorption trenches and once there it blocks them up. This is called carry-over and we try to prevent it.
When you go to empty the sludge and clean-up we don't want any of the contents leaving the septic tank. So it is a simple matter of tilting the sludge judge and tipping the contents back into the main tank.
Properly maintained, septic systems can work effectively for many years.
Fact sheets about maintaining your septic system are available on council's website.