Looking after a septic tank or treatment plant

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Septic tanks and home sewage treatment plants both rely on bacteria to break down household waste. Most problems owners run into come from three things: putting the wrong things down the drains, sending too much water through the system at once, and damaging or overloading the land application area (the part of the yard where treated effluent goes).

The points below are drawn from the published guidance of three south-east Queensland councils: Toowoomba Regional Council (opens in a new tab) (the Lockyer Valley's western neighbour), City of Moreton Bay (opens in a new tab) and Logan City Council (opens in a new tab). The conditions on your own system's approval come first. Lockyer Valley Regional Council's plumbing team (1300 005 872) can tell you what's on record for your property (council (opens in a new tab)).

Keep these out of the drains

• Wipes, sanitary products, plastics, coffee grounds, bones and glass. They don't break down and can block the tank, pumps or outlet filter.
• Food scraps, milk, fats and oil. Use a sink strainer and wipe greasy pans before washing. Toowoomba council also says not to use a garbage grinder unless your system is designed for one.
• Chemicals, paint, thinners, pesticides and harsh cleaners. Bleach, disinfectants and ammonia can kill the bacteria the system depends on. Logan council notes that without enough bacteria the tank may not treat waste properly, which causes odour.

Use toilet paper that breaks down easily and biodegradable, septic-safe products. Logan council suggests natural cleaning products and low-phosphorus detergents. If you're not sure about a product, ask your service agent.

Go easy on water

• Fix leaking taps and toilets promptly.
• Spread out washing loads, baths and other big discharges. Moreton Bay council notes excessive water can temporarily overload a system.
• Don't let roof water or surface runoff into the system.

Protect the land application area

• Keep cars, trailers, play equipment and heavy items off it, and don't drive over any part of the system.
• Don't build over it, pave it, or plant trees that shade it. Keep the grass mown.
• Don't use it for growing food, keeping pets or children's play.
• Keep sprinklers and hoses where they were approved. Moving or extending them outside the approved area needs a new design and permit, according to Toowoomba council.
• Effluent must stay on your property. It mustn't run onto a neighbour's land, into gutters or towards waterways.

Don't switch it off

Toowoomba council lists switching a treatment plant off to save power as something not to do. Don't cover tanks with soil or mulch that blocks access for servicing, and keep lids sealed against mosquitoes and vermin.

Signs it needs attention

Moreton Bay council lists these as signs a system needs attention:

• toilets and drains draining slowly, or wastewater backing up
• a rotten-egg smell near the tank or disposal area
• water pooling in or near the disposal area
• poor plant growth, or patches of unusually dark green grass, over the disposal area
• a treatment plant alarm going off

Call your service agent, or a licensed plumber, rather than ignoring an alarm. Toowoomba council's guidance is not to make repairs or alterations without council approval, so fixes beyond routine care aren't a DIY job.

Routine care

• Treatment plants: need regular servicing by a licensed service agent. For aerated plants this is commonly every three months. See Servicing and maintenance.
• Septic tanks: Toowoomba council's guidance is to clean the outlet filter every three months and have the tank desludged every three to five years by a licensed liquid waste contractor.
• Keep a record of your system's model, your service agent, the service history and any parts replaced.

If your system is failing or you're adding to the house, see Replacing or upgrading a septic system.