What does an overflow relief gully actually do?
The overflow relief gully, or ORG, is your home's sacrificial spill point: it exists to flood your garden so the sewer never floods your bathroom. It is the round or square grated fitting in the yard, usually near an outside wall close to the bathroom or laundry, connected directly to your sanitary drain. Its grate is deliberately set below the level of your lowest indoor fixture and above the surrounding ground. If the sewer line blocks and backs up, the rising sewage reaches the ORG first, pops the loose grate, and discharges outside. Without a working ORG, the same backup arrives at your lowest shower grate or toilet, inside the house. AS/NZS 3500.2 sets out these level and location requirements for exactly that reason.
Why is my ORG overflowing on a dry, sunny day?
A dry-day overflow means your sewer drain is blocked, and because it is on your side of the connection, clearing it is the property owner's responsibility. The water and waste your own household is sending down the drain has nowhere to go, so it is rising back up and escaping at the relief point. This is the ORG doing its job, but it is also an urgent warning: keep using water and the sewage keeps coming. Stop running taps, washing machines and toilets, and get the line cleared. As of 2026 a machine drain clear on the Gold Coast is $250 to $400, and a CCTV camera add-on at $120 to $180 while we are on site shows what caused it, which in our experience is usually tree roots in older pipework.
What if it only overflows during heavy rain?
Rain-triggered overflows point to a different set of causes, and responsibility depends on which one you have. In heavy storms, the wider sewer network can surcharge, pushing flow back toward private properties; that side of the system belongs to the service provider. But rain can also expose problems on your side: stormwater illegally or accidentally connected into the sanitary drain, or groundwater pouring into cracked sewer pipes and overwhelming them. Here is how to read the symptoms:
| Symptom | Most likely meaning | Whose problem |
|---|---|---|
| ORG overflows on a dry day | Blockage in your sewer drain | Yours to clear |
| ORG overflows only in heavy rain | Network surcharge, or stormwater entering your sewer | Provider, or yours if cross-connected |
| Gurgling fixtures plus a smelly ORG | Partial blockage building in your line | Yours, and worth clearing early |
| Sewage inside the house, ORG never spilled | ORG blocked, buried or altered | Yours, and urgent to fix |
A CCTV inspection, $200 to $350 standalone as of 2026, settles the question by showing whether your line is sound.
Can I cover, raise or pave over my ORG?
No. Covering, raising or sealing an ORG disables the one fitting protecting the inside of your home, and it breaches the standard the fitting is installed under. We regularly find ORGs buried under new turf, decked over, paved to the same height as the surrounding ground, or fitted with a glued-down grate to stop smells. Every one of those turns the next blockage into an indoor spill of raw sewage, with the cleanup and insurance argument that follows. The grate must stay loose so it can lift, the surrounds must stay below indoor fixture level, and nothing should sit on top of it. Landscapers are the usual culprits here, so if you are renovating the yard, tell them where the ORG is and that its levels are protected under AS/NZS 3500.2 and the Plumbing and Drainage Act 2018.
What should I do right now if sewage is coming up the gully?
Stop adding water, keep people and pets away from the overflow, and call a plumber before touching anything else. Every flush and load of washing adds to what is surfacing in your yard. If the overflow is sewage from the wider network rather than your own use, phone your water service provider as well, because network surcharges are their responsibility to attend. Once the line is cleared, hose the affected area and treat it with disinfectant, keeping runoff out of stormwater pits. If it has happened more than once, get the camera down the line, because repeat surcharges mean roots or damage that a clear alone will not fix, and options like relining at $400 to $600 or more per metre exist precisely for that pipe.
How do I know my ORG is set up correctly?
A correct ORG has a loose grate, sits below your lowest indoor fixture, stands above the surrounding ground, and is not smothered by pots, decking or garden beds. If yours is buried, sealed, level with the lawn, or you cannot find one at all, have it checked. Older homes are sometimes missing a compliant ORG entirely, and drainage alterations are licensed work under the Plumbing and Drainage Act 2018, so correcting one is a job for a licensed plumber. It is a small fitting, but it is the difference between hosing down the garden and ripping up sewage-soaked carpet.
ORG overflowing or smelling? Call Hills Plumbing & Gas on 0472 657 042. Fast attendance across the Gold Coast, fixed price quoted before we start, QBCC licence 15243081, 5.0 stars from 27 Google reviews. See our blocked drains service.