What Gully Traps Do
A gully trap is basically a U-bend pipe linking your house drains to the council sewer. It connects to your kitchen, bathroom, and laundry drains. That U-bend stays filled with water, creating a barrier that stops sewer gases entering while wastewater flows out.
The 150mm Rule You Need to Know
Victorian plumbing regulations have specific height requirements for overflow relief gullies. These aren’t optional. Your ORG riser’s spill level has to sit at least 150mm lower than the lowest fixture draining into your system. For most Brighton houses, that’s either the shower grate or a floor waste.
Why exactly 150mm? This gap makes sure sewage hits your external ORG and spills outside before it can rise high enough to come back through your shower, toilet, or other fixtures inside. If you’ve got less than 150mm separation, your ORG won’t work. Sewage reaches your internal plumbing first, which defeats the whole point.
Licensed plumbers and drainers have to figure out overflow relief gully levels before any drainage work kicks off. This usually means working with builders to calculate levels based on the slab floor and where the finished ground will end up.
Not sure if your Brighton property meets these requirements? Ezy-Plumb can check your drainage system and make sure your ORG sits where it should according to Victorian standards.
The 75mm Ground Height Rule
Height requirements work in both directions. Your ORG needs to sit lower than internal fixtures, but it also needs to sit high enough above the ground around it. Specifically, the overflow relief gully riser has to be at least 75mm above the finished surface level. This stops stormwater getting in.
If your ORG sits too low or level with the ground, heavy rain just floods stormwater straight into your sewer system. This creates problems. Sewers can’t cope with massive rainwater. Extra water causes blockages and overflow risk across the system, hitting neighbors' properties too.
Gully risers in paths must finish level with the surface to stop ponding. The surface needs sloping away so stormwater runs off, not in. Getting these levels sorted requires plumbers, drainers, and builders to plan things out properly right at the start of your project.
Riser Heights and How They’re Installed
Floor waste gully risers inside buildings have their own rules. The Victorian Building Authority says floor gully riser height, measured from the top of the water seal to the floor surface, can’t go over 600mm. You can extend to 1m only where the gully riser gets plant room discharges exclusively and the gully’s located above ground floor.
Risers from gullies have to be installed straight up and down with no offsets. This stops drainage problems and makes sure the system works how it’s supposed to. Install it wrong and you get blockages, poor drainage, and potentially the BPC taking action.
Planning renovations in Brighton that involve plumbing work? Ezy-Plumb sorts out all aspects of compliant gully trap installation including working out heights, coordinating with builders, and getting necessary approvals from council and the Building and Plumbing Commission.
Mistakes That Happen All the Time
Covering ORGs with tiles, concrete, decking, or paving is probably the most common one. The grate has to pop off easily when pressure builds. Anything stopping this ruins the safety mechanism.
Builders sometimes leave ORG risers higher than needed so paving contractors can cut them down to match the finished path height. When paths turn into DIY jobs or get done by contractors who don’t know what they’re doing, the ORG often ends up at the wrong height. Installing paths too close to the damp-proof course usually results in ORGs sitting too high to hit that 150mm separation requirement.
Some renovations box in part of a building’s original outside wall over an existing gully without putting another compliant ORG somewhere else. This leaves the property without proper overflow protection. Properties built before 1976 might not have ORGs at all unless plumbing got upgraded after that. These older houses sometimes have disconnector gullies or vents that can get converted to compliant ORGs by licensed plumbers.
Looking After Your Gully Trap
Property owners are responsible for maintaining gully traps and ORGs from the house to where it connects to the sewer. Regular maintenance is pretty straight forward but you’ve got to actually do it. Flush your gully trap every month with hot water and dish soap. Vinegar and baking soda works well for breaking down grease and soap buildup. Check grates regularly and clear out leaves, hair, or whatever else gets stuck there.
Don’t put pot plants, garden furniture, or storage stuff over your ORG. The area around it needs to let overflow drain away from your house foundation. Keep the gully accessible so you can clean it easily and pressure can release properly when it needs to.
If sewage overflows through your ORG, that’s telling you there’s a sewer blockage needing immediate attention. Call Ezy-Plumb straight away to clear the blockage before damage gets worse.
What the Regulations Say
Gully trap installation in Victoria is regulated as either drainage work or sanitary work under the Plumbing Regulations 2018. The Plumbing Code of Australia, which these regulations adopt, sets the technical requirements all installations have to meet.
The Building and Plumbing Commission enforces these requirements. They can issue improvement notices, prohibition notices, and prosecute for non-compliant work. Non-compliance also messes with your insurance coverage. Most policies won’t cover damage from improperly installed or maintained drainage systems.
Get It Right the First Time
Correct gully trap installation protects your Brighton property from sewage backups, preserves value, and ensures Victorian compliance. Height requirements reflect real drainage performance during blockages.
Licensed plumbers understanding the requirements and coordinating with other trades install gully traps correctly the first go.
For Brighton gully trap installation, compliance verification, or maintenance, call Ezy-Plumb on 0402 169 096. We handle initial checks through final certification.
FAQs
Q1: Can a gully trap freeze in winter?
Very unlikely in Brighton. Winters aren’t cold enough for that.
Q2: Do older Brighton homes need overflow relief gullies?
Properties built before 1976 often don’t have ORGs unless the plumbing’s been upgraded, but they can be retrofitted by licensed plumbers.
Q3: Should rainwater go into a gully trap?
No. It’s only meant for wastewater from the house.
Q4: Is it bad if plants grow around the gully?
Small plants are fine. Just don’t block the grate.
Q5: Can a cracked gully trap cause smells?
Yes, it can. If the trap or pipe cracks, sewer smells can escape.
