Connecting to town sewer: what happens to the old septic tank?

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Sewer networks in parts of the Lockyer Valley have grown. Around Plainland, for example, Urban Utilities has upgraded the wastewater network as part of its Plainland to Laidley upgrades (Urban Utilities project page (opens in a new tab)). If sewer now runs past your property, connecting can mean no more pump-outs, servicing contracts or disposal area to look after. It also leaves an old tank in the ground that has to be dealt with properly.

Step 1: confirm sewer is available to your lot

Urban Utilities is the water and sewerage provider for the Lockyer Valley (Urban Utilities (opens in a new tab)). A sewer main in the street doesn't always mean your lot can connect, so check with Urban Utilities for your exact property, including where the connection point is.

Step 2: get the approvals sorted

Connecting a house to sewer and decommissioning an on-site system are both plumbing and drainage work for a licensed plumber and drainer. Toowoomba Regional Council, the Lockyer Valley's western neighbour, says a plumbing approval is needed before any decommissioning work begins (Toowoomba Regional Council (opens in a new tab)). In the Lockyer Valley, ask Lockyer Valley Regional Council's plumbing team (1300 005 872) what they require for your property (council (opens in a new tab)). Your plumber will usually handle the paperwork.

Step 3: decommission the old system properly

An abandoned tank that's simply left can collapse, hold stagnant sewage, or be a hazard to children and animals. Toowoomba Regional Council publishes these steps for decommissioning:

1. Get a plumbing approval for the work.
2. Have all effluent and sludge pumped out by an approved liquid waste contractor. Keep the receipt, because council may ask for it.
3. Treat the empty tank with agricultural lime or hydrated lime.
4. Punch one or more holes in the bottom of the tank so it drains.
5. Remove concrete lids and break the tank walls below ground level.
6. Fill the tank with crusher dust and compact it to the surface. Top it up if it settles.

Those are Toowoomba's published steps. Lockyer Valley council sets its own conditions, so confirm what applies before work starts. Treatment plants have more parts (pumps, blowers, irrigation lines and electrical connections), so ask your plumber how each will be dealt with, including disconnecting the power safely.

Things to sort out with your plumber

1. Who confirms the connection point with Urban Utilities?
2. Who lodges the approvals, and what inspections are involved?
3. Does the quote include the pump-out, the decommissioning and making the ground safe, or only the new connection?
4. What happens to the old disposal area and irrigation lines?
5. Will I get paperwork showing the old system was decommissioned? (It's useful when you sell.)

Until you're connected, keep looking after the existing system and keep any servicing up to date. See Looking after your system.

For local notes, see Plainland, Hatton Vale and Kensington Grove and Gatton.