Where does my pool backwash go, and why do my drains overflow?
When you backwash a pool filter, a lot of dirty water comes out of the waste line fast. It has to go somewhere, and in Sydney the answer is the sewer, not the garden, the street or the stormwater, because it carries chlorine, salt and dirt that shouldn't reach waterways. If your drains gurgle or overflow while the pool is backwashing, the connection or the sewer line isn't coping. Here's how it should work and how to fix it.
Where backwash should go
- Into the sewer, through a proper connection such as a dedicated pipe to a gully or sewer point.
- Not into stormwater pits, the kerb or neighbouring properties. Stormwater goes straight to the beach untreated.
- Not onto the lawn or garden, especially salt pools, which can kill plants and soak into neighbours' yards.
Why drains overflow during backwash
Too much, too fast
A powerful pool pump can push more water than a small gully or pipe can take, so it backs up and overflows.
Partial blockage
Roots or build-up in the sewer line slow the flow. Normal use copes, but a backwash overwhelms it.
Gurgling inside
The rush of water pushes air back through traps in the house, so sinks and toilets gurgle. See gurgling drains.
Poor connection
Backwash hoses lying in a gully, or a connection that's too small or badly placed.
How we fix it
- Clear and camera-inspect the sewer line to remove any partial blockage.
- Install or upgrade a proper backwash connection to the sewer, sized for your pump.
- Add a suitable receiving point so backwash doesn't splash or overflow.
Backwashing for shorter periods, or at a lower flow, can help in the meantime. You get a fixed price before any work starts.
In southern Eastern Suburbs homes
Many pools in Maroubra, Matraville and Malabar were added years after the house, and the backwash was simply run to the nearest gully. Combined with old clay sewer pipes, that's a common source of overflowing gullies on backwash day.
Why locals call us
- Local to Matraville and the southern Eastern Suburbs
- Free on-site quotes, with a fixed price before any work starts
- Lifetime labour warranty on our workmanship
- 100+ five-star Google reviews
- Licensed plumbers and gasfitters (Lic. 398171C)
Common questions
Where should pool backwash water go?
Into the sewer through a proper connection, not into stormwater, the street or the garden.
Why does my gully overflow when I backwash the pool?
The backwash flow is more than the connection or sewer line can take, often because of a partial blockage.
Can I backwash my pool onto the lawn?
It isn't recommended, especially for salt pools, and water mustn't run onto neighbouring properties or into stormwater.
Can a backwash connection be upgraded?
Yes. A properly sized connection to the sewer stops overflows.
Related help: gurgling drains, blocked drains, drain jetting and where does sewage and stormwater go? Local pages: Maroubra, Matraville, Malabar and Coogee.