Heavy rain overloads the sewer, and your drains feel it
Sewer and stormwater are separate systems, but heavy rain finds every crack between them. When a Queensland storm dumps serious water, some of it gets into the sewer network through damaged pipes, illegal connections and leaky manholes across the whole suburb. The sewer main runs fuller than it was designed for, a condition called surcharge, and the pressure backs up into the private drains connected to it, yours included. Air gets pushed back through the system, traps bubble and smell, and in the worst cases sewage rises at the lowest fixtures. If your drains only misbehave during or just after big rain, surcharge is the first suspect.
The overflow relief gully is doing its job
Somewhere outside your house, usually near a bathroom or laundry wall, is an open grated fitting called the overflow relief gully, or ORG. It is deliberately set lower than your indoor fixtures so that if the sewer backs up, it overflows there, in the yard, instead of through your shower. If you see water or sewage coming up at the ORG during rain, that is the system working as designed, but it is also a clear signal that the sewer beneath you is surcharged or blocked. Keep the ORG clear of pot plants, paving and garden beds, because a covered ORG sends the overflow to the next lowest point, which is inside your house.
Cracked pipes let stormwater in, and that is a private drain problem
Suburb wide surcharge passes when the rain does. But if your drains back up in moderate rain when the neighbours are fine, the likely cause is on your side of the boundary: cracked or root damaged sewer pipes on your property letting groundwater and stormwater flood in. Your drain effectively becomes a stormwater collector, carrying water it was never sized for, and any partial blockage that was harmless in dry weather becomes a backup in the wet. This is the classic pattern behind "it only blocks when it rains", and in our experience it is the most common finding when we put a camera down a rain sensitive Gold Coast drain.
Dry and siphoned traps cause the smell without any backup
If the symptom is smell alone, sniff out the floor wastes. A surcharging sewer can push or siphon the water out of trap seals, and a floor waste in a spare bathroom can simply dry out between uses. Either way, the empty trap lets sewer gas straight into the room. The free fix is to pour a jug of water into every floor waste and unused drain, wait a day, and see if the smell is gone. If it returns with the next rain, the venting or the drains need proper investigation.
| Symptom after rain | Likely cause | What we do, as of 2026 |
|---|---|---|
| Smell at floor wastes, no backup | Siphoned or dry trap seals | Refill traps yourself first, investigate venting if it recurs |
| Gurgling and slow drains during rain | Sewer surcharge or partial blockage | Machine clear $250 to $400 if it persists after rain |
| Water rising at the ORG | Surcharged or blocked main | Urgent clear, camera add-on $120 to $180 to confirm cause |
| Backs up in moderate rain, neighbours fine | Cracked pipes taking in stormwater | CCTV inspection $200 to $350, then repair options off footage |
| Repeat backups every storm | Structural damage or roots | CCTV plus jetting plus report, $500 to $900 |
Your drains or the council main: who is responsible
The dividing line matters for your wallet. Drains on your property up to the connection point are the owner's responsibility; the sewer main itself belongs to the network operator. If our camera shows your pipes are sound and the problem is the main surcharging, we tell you exactly that, give you the footage, and you take it to the City of Gold Coast rather than paying us to fix pipes that are not broken. If the fault is on your side, you get a fixed quote with the evidence on screen.
Sources: Plumbing and Drainage Act 2018 (Qld); City of Gold Coast water and sewerage responsibility guidance.
Drains playing up every time it rains?
Book a CCTV inspection before the next storm instead of after it. Hills Plumbing & Gas inspects and clears rain affected drains across the Gold Coast, $200 to $350 for CCTV as of 2026, fixed pricing quoted up front. QBCC licence 15243081. Call 0472 657 042 or book through our blocked drains service page.