Blocked drain Bondi: strata grease job

The call came from a strata block in Bondi with a blocked drain and sewage coming up out of the gully in the side passage. By the time we arrived it had spread down the concrete between the building and the fence, which is the only way through to the back of the property. Every unit in the block drains into that one line, so until it was cleared, nobody upstairs could safely run a tap or flush a toilet.

The cause turned out to be grease. Not a single bad night of cooking, but years of fat and oil from the kitchens above, set hard on the inside of the shared sewer until there was nowhere left for the water to go.

Why a blocked drain in a Bondi strata block overflows outside

The gully in the side passage is the lowest opening on the drainage system, set below the floor wastes and toilets inside the units. When the line downstream of it blocks, wastewater backs up and comes out at the lowest point first. That is by design. It means the overflow happens outside on the concrete rather than through a bathroom floor in a ground floor unit.

So an overflowing gully is the warning, not a second fault. It tells you the line is blocked somewhere between that gully and the sewer main, and that every fixture feeding into it is about to have nowhere to drain.

How grease blocks a shared sewer line

Fat and oil go down the sink warm and liquid. Once they hit the cooler pipe they set, and they stick to the pipe wall. Sydney Water's guidance is plain about it: fats, oils and grease solidify in pipes and can eventually cause major blockages, and only water, detergent and soap should go down the sink.

In a house, one kitchen feeds the line. In a strata block, every kitchen in the building feeds the same pipe. A little pan fat from each unit, week after week, adds up to a lot of grease in one place. The build-up narrows the pipe a little at a time, so nothing seems wrong for years. Then food scraps or wipes catch on the narrowed section and the line closes over.

That is why grease blockages tend to arrive as an emergency. The pipe was fine yesterday, at least as far as anyone could tell, and today it is overflowing.

Clearing the blocked drain: jetter first, then the camera

We set the high pressure jetter up at the gully and fed the hose down the line. Jetting is the right tool for grease. A mechanical cable can punch a hole through a grease blockage and get water moving again, but it leaves most of the fat stuck to the pipe wall, and the line closes up again soon after. The jetter's water pressure scours the wall clean along the whole run.

Once the line was flowing, the CCTV camera went down it. That step matters on a strata job. It confirms the line is properly clear rather than just draining for now, and it shows whether the pipe itself is sound or whether there is a crack, a sag or root entry that helped the grease catch in the first place. A committee deciding what to do next needs to know which of those it is dealing with.

The passage was then washed down so residents could use it again. Out on the street, signs and safety cones stayed out for as long as hoses were running across the footpath.

Who pays for a blocked sewer in a strata building

A sewer line that carries waste from more than one unit is generally common property, not any one owner's pipe. Under NSW Government guidance on strata repairs and maintenance, the owners corporation is responsible for maintaining and repairing common property. In practice that means the strata manager or committee arranges and pays for clearing a shared line, even when the overflow shows up next to one particular unit.

Where the blockage sits also matters. The private line on the property side of the connection belongs to the building. If the blockage turns out to be in the Sydney Water main in the street, it is theirs to clear. A camera inspection settles that question quickly.

Stopping grease blockages in Bondi apartment blocks

Bondi has a lot of red brick walk-ups with a narrow passage down the side, a gully near the back, and one sewer line serving every unit. The plumbing in many of them has been in the ground for decades, and older lines with rough joints give grease more to grip on.

The fix that lasts is mostly about what goes down the sinks. A short note from the strata manager to every resident after a blockage like this does more good than most people expect, because most residents have no idea the pipe under their kitchen is shared with the whole building. Sydney Water suggests wiping greasy pans with a paper towel before washing them, and pouring fat and oil into a container that goes in the bin once it is full.

For a block that has had more than one grease blockage, scheduled jetting is worth considering. Clearing the line on a plan, before it closes over, is cheaper and far less disruptive than clearing it in an emergency with sewage across the passage.

Warning signs before a strata drain blocks

• Ground floor units draining slowly first. They sit closest to the shared line, so they feel a narrowing before anyone upstairs does.
• Gurgling from a floor waste or toilet when another unit drains. That is air being pushed past a restriction in the shared pipe.
• Water sitting in the gully grate in the side passage. A gully should be clear. Standing water in it means the line beyond is slow.
• A sewer smell around the side passage or back of the block. Grease and trapped waste sitting in a slow line give off an odour before an overflow.
• A previous blockage in the same line. Grease clears, but the habits that caused it usually haven't changed.

How to reach Norton Plumbing

Norton Plumbing has worked in Bondi and across the Eastern Suburbs since 2019, on blocked drains, drain jetting, CCTV inspections, pipe relining and strata plumbing. I hold NSW plumbing licence 397768C. The team works out of 10/11a-15 Berwick St, Coogee. If the drain at your building is overflowing, or a shared line keeps blocking, see our blocked drains page, our strata plumbing page, our Bondi plumber page, or call 0477 858 951. Quotes are free across the Eastern Suburbs.