How will I know if my septic tank system has been affected?
Cyclones, flood waters or heavy rain may affect or damage your septic tank system, also known as an onsite wastewater system.
This includes
- septic tanks (primary treatment systems),
- secondary treatment systems (STS), aerated wastewater treatment systems (AWTS), and their land application systems, for example plastic leach drains, sprinklers and below ground drippers and connection pipes.
Septic tank systems typically comprise a concrete, plastic or fibreglass tank.
Most septic tanks should not be structurally damaged by flooding as they are below ground.
However, flood water may enter your septic tank system through the toilet, other fixtures or the overflow relief gully grate.
Flooding of the septic system may wash out solids from the tank causing blockages or system damage.
Safety issues that need to be checked:
- open covers/pits
- ruptured/leaking systems (including pipes)
- damaged/exposed pipes that may need capping/sealing off.
- failed systems are not easy to identify. However, some simple indicators may include:
- a pungent odour around the tank and land application area
- blocked fixtures, with wastewater overflowing from the relief point
- high sludge levels within the primary tank
- sewage flowing up through the toilet and sinks.
Some onsite wastewater treatment systems may rely on mechanical and electrical equipment, such as pumps, aerators and filters.
This equipment may be damaged by flood or loss of power.
To prevent injury or further damage to your system contact your wastewater service agent.
What can happen to the septic tank during a flood?
Flooding of the chambers in the septic tank or primary/secondary treatment tanks can lift the floating crust. This naturally forms on top of the wastewater and includes:
- fats
- grease
- other materials.
If the tank becomes flooded, the crust can lift and then block either the inlet or outlet of the septic tank pipes.
This may cause solids to transfer from the septic tank to the leach drain or disposal system.
In addition, septic tanks, leach drains, pump pits and irrigation pipework can fill with silt and debris.
This will either reduce the capacity or the effectiveness of the treatment system.
What should I do if my septic tank has been under flood water?
Do not use any toilets, laundry, kitchen, bathroom or clean-up equipment connected to the onsite wastewater disposal system until:
- all parts of the wastewater treatment and disposal system have been professionally inspected and repaired
- your onsite wastewater disposal system has been approved for use by the local authority environmental health officer.
Contact your local authority environmental health officer for more information.
What should I do if my on-site wastewater system has been damaged by bushfire?
Only trained specialists are suitably equipped to clean or repair onsite waste disposal systems.
This is because tanks may contain dangerous gases and other harmful materials.
Contact your local authority environmental health officer for a list of wastewater disposal system contractors who work in your area.
Onsite wastewater disposal systems should be pumped out by a licensed septic tank operator as soon as possible after the flood.
However, it is important to ensure that the water level in the ground surrounding the tanks is as low as possible before you start.
It is possible for empty tanks to float out of the ground causing damage to underground pipework.
Aerated wastewater treatment system
Aerated wastewater treatment systems (AWTS) should not be used if it has been inundated with floodwater.
Isolate the electrical connection and call the service technician immediately.