New septic systems in the Lockyer Valley

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A conventional septic system is the simplest type of on-site sewerage facility. Wastewater settles in a tank: solids sink as sludge, oils and grease float as scum, and the partly treated liquid flows out to buried trenches or beds where the soil finishes the job. There's no aerator or pump in a basic gravity system. That means fewer moving parts and no compulsory three-monthly service, but it relies on your soil being suitable.

Will a septic system suit my block?

That's decided by the site and soil evaluation, not by preference. If the soil can't absorb and treat the effluent safely, or the block is too small for the trench area needed, the designer may specify a treatment plant instead (see Home sewage treatment plants). Setbacks from buildings, boundaries, bores and waterways also limit where the disposal area can go.

Approval steps

• A qualified person carries out the site and soil evaluation and prepares the system and drainage design.
• Your plumber lodges a permit application with Lockyer Valley Regional Council using the state's Form 1. Council has opted out of fast-track plumbing applications, so allow time for assessment.
• A septic-only (primary) system doesn't need a state treatment plant approval. Treatment plants do.
• Installation is by a QBCC-licensed plumber and drainer, followed by council inspection.

Sources: Business Queensland (opens in a new tab); Lockyer Valley Regional Council – Forms and Fees (opens in a new tab); QBCC – who must hold a licence (opens in a new tab).

What affects the cost

Only a quote after a site inspection is reliable. We don't publish prices because they depend on your block. These are the things that move the price, and the ones to check line by line on any quote:

• Site and soil evaluation and design: a separate professional service in most cases. Ask whether it's included.
• Council permit and inspection fees: set by Lockyer Valley Regional Council's adopted fees and charges (council forms and fees (opens in a new tab)).
• Size of the trench or bed: this follows from your soil. Poorer-draining soil needs a larger area.
• Excavation conditions: rock, slope, wet ground and machinery access.
• Tank: material, size, delivery and craning if access is tight.
• Distance and fall: how far the tank and disposal area are from the house, and whether gravity flow is possible or a pump is needed.
• Decommissioning: pumping out and filling or removing an old tank.
• Making good: backfill, turf and repairs to driveways or gardens.

Looking after it

Toowoomba Regional Council's guidance for owners is to have the septic tank desludged every three to five years by a licensed liquid waste contractor, and to keep the land application area mown and clear. That's a useful rule of thumb for the Lockyer too, but your system's design or approval conditions come first.

Questions to ask before you hire

1. What's your QBCC licence number? (Check it on the QBCC register.)
2. Who is doing the site and soil evaluation and design, and is it in this quote?
3. Does the price include council fees, the tank, trenches, backfill and making good the site?
4. What happens if you hit rock or groundwater during excavation?
5. How long do approval and installation usually take from here?
6. What warranty do you give on workmanship, and what does the tank manufacturer give?