My septic tank

GMB Water’s contractor, Veolia, will pump out your septic tank every five years. This service is included in your wastewater service charge, which appears on your rates notice. If your tank isn’t emptied during the scheduled program, you may need to arrange and pay for a contractor yourself to avoid blockages or plumbing issues between services.

Note: If your septic tank is connected to GMB Water's CWMS you should organise to have your septic tank pumped out every five years. 

To complete the pump-out, the contractor will need clear access to your septic tank. Hatch lids are usually around 800mm x 600mm and need at least 150mm of clearance around the edge. Please don’t remove the lid yourself. If you’re unable to locate or uncover it, contact Veolia to discuss your options. For tanks located well below ground level, we recommend installing an approved access shaft and cover to make future pump-outs safer and easier.

Over time, all septic tanks wear down, especially those made of concrete. Many tanks in the region are now over 50 years old and may need repairs, replacement, or decommissioning in the years ahead.

Some tanks are located at ground level, while others have access shafts with lids. They’re often covered by mulch or plants and may be hard to spot. Some properties have a full septic system with soakage tanks; others just have a single tank connected to the Community Wastewater Management System (CWMS).

If your tank is ageing, it’s worth checking that the lids are visible, safe, and in good condition.

When contractors notice damage, like cracks, crumbling concrete, or unsafe lids, they’ll report it to Council. The Environmental Health team will then assess the issue and contact you to discuss next steps. If your property can be connected to sewer, this may be offered as an option.

Tanks that are no longer in use should be safely decommissioned to prevent collapse.

The following points will help ensure correct operation of your septic tank system and help extend the life of the system. 

• Use toilet paper that readily breaks down. Do not flush sanitary napkins, tampons, wipes (including those that say "flushable" disposable nappies, etc down the toilet as these items do not break down and will cause the septic tank to block.
• Household detergents and bathroom products should be biodegradable. Use products labelled as 'septic tank safe' and use only as recommended.
• Disposal of cooking oils and fats down the drain may cause blockages in the system. Dispose of these by placing them in a sealed container and putting them in the general rubbish bin. Thoroughly scrape all food scraps, oil and fat residue from plates, dishes, saucepans etc before washing them. 
• Avoid fitting food waste disposal units. Instead, compost raw vegetable materials in a compost bin or worm far. 
• Unused medicines and pharmaceutical products should not be correctly disposed of and are not allowed to enter the septic tank system. 
• Do not discharge commercial or industrial waste such as paints and petrol products into the septic system. 
• Ensure storm water, including rainwater tank overflows and surface run off, does not enter the septic tank system
• Backwash water from swimming pools and spas must not be discharged into the septic tank. In Community Waste Management Service (CWMS) areas the discharge is to be connected after the septic tank via a gully trap. Where CWMS is not available, the discharge is to be directed toa below ground agricultural drain or subsurface soakage trench. 
• Relef valves on mains pressure hot water services should be activated every 2-3 months to prevent valve failure and the constant dripping of water into the septic tank system. 
• All vents and inspection openings into the drain and septic tank should be properly sealed to prevent access of mosquitos. 

The most common reason for a blockage is the collection of material at the inlet point of the tank. In older tanks there is a cleaning point at the inlet of the tank. More recently made tanks have an inspection point over the inlet point. Plunging either of these points will release the built up material and clear the blockage. 

If your house has old style earthenware drains there is a higher possibility of blockages due to intrusion of tree roots. Houses with PVC drains are less likely to suffer from this sort of problem. An older septic tank may also become blocked due to root intrusion. Experience has show that a septic tank can comfortably survive five years between pump outs. If a blockage occurs before then it is likely to be a blockage at the inlet point of the tank. Plunging of the inlet point as described above will clear the blockage in most cases. 

It is not always possible to clear a blockage yourself an in many cases the assistance of a plumber will be necessary. 

It is normal for a septic tank system to give off some odours. Most odours originate from the septic tank and discharge through the head vent. People may or may not notice odours depending on the location of vents on the house. 

Common causes of odours are listed below.

• Calm weather conditions can emphasise odour problems for a longer period of time.
• Verandahs, pergolas, high fences etc, in the vicinity of the head vent can trap any unpleasant odours, particularly on calm days. 
• Sometimes odours may come from a neighbour's vent if dwellings are within close proximity. 
• Odours may be escaping from a septic tank lid or inspection point situated at ground level rather than from a vent.
• Heavy water usage (e.g when clothes washing) may agitate the septic tank contents causing a surge in odours.
• Odours can be exacerbated after the tanks has been recently pumped out. This is due to the fact that the primary chamber of the tank has not developed enough microbiological activity. 

Note: Unpleasant odours are not a health risk and do not necessarily mean that the septic tank needs pumping out. 

In most cases steps can be taken to stop or reduce odour problems:

• The vertical height of the head vent can be extended by a metre or so to allow odours to discharge at a high level.
• If more than one vent exists on a house an 'air admittance calve' can be fitted. These devices allow air into the system but do not allow air to escape. They are available from plumbing suppliers. 
• Vents of 75mm to 100mm diameter can be reduced to 50mm to reduce the amount of odours being discharged.
• Sometimes a 'sour' odour may indicate a low pH in the tank. To fix this, 500g hydrated lime can be flushed into the septic tank 3-4 times a year via the toilet pan, which will raise the pH of the septic tank contents. 
• Commercial products which balance the microbial activity in the tank and reduce odours are available. 
• Ensure all inspection points and septic tank lids are adequately sealed to prevent odours from escaping. 
• If odours are noticed inside the house it is most likely due to a loss of water seal in the toilet or floor traps. Flushing the toilet or running water into a basin will replace the seal, causing the odours. Unfortunately there is no simple solution to prevent the loss of the water seal toilets and floor traps. 

Please complete the form for any septic tank enquiries. Alternatively, you can contact Veolia direct on (08) 8398 2484.