Know your system
Types of sewage system
If you're off the main sewer, your waste is handled by one of a handful of systems — or a combination of them. Here's what each one is, how it works, and what it needs from you to keep working and keep the river clean.
First, the big idea
Treat, then disperse
Most off-mains setups have two jobs: treat the waste, then disperse the cleaned water back to the environment. Some units do one job, some do both — and one just stores. Knowing which parts you have tells you what care they need.
Breaks down the waste so the water leaving it is cleaner. Some treat fully, some only partly.
Returns treated water safely to the ground, where soil finishes the job. Always paired with a treatment stage upstream.
Holds the waste with no treatment and no outlet. Everything has to be tankered away.
A septic tank almost always pairs with a drainage field — the tank treats, the field disperses. A package treatment plant treats so thoroughly it can often discharge straight to a stream. A cesspool does neither — it just holds everything until a tanker empties it.
The systems
Find yours
Tap any system to see a full rundown — including how it copes with busy weekends, what not to pour down it, and the signs it's struggling.
Septic tank
The most common off-mains system
An underground tank that settles out solids, then sends the liquid to a drainage field to soak away.
Learn more → Treats the wastePackage treatment plant
Sewage treatment plant — e.g. Klargester, BioDisc
Like a septic tank, but with a powered stage that fully treats the waste — clean enough to discharge to a watercourse.
Learn more → Stores onlyCesspool
Also called a cesspit — a sealed holding tank
A sealed tank that just stores sewage with no treatment and no outlet — it has to be emptied by tanker.
Learn more → Disperses the waterDrainage field
Also called a soakaway or infiltration field
Not a tank — a network of buried pipes that lets treated water soak into the soil, where bacteria finish the job.
Learn more → Treats the wasteFilter / clinker bed
Trickling or percolating biological filter
A bed of stone or clinker that settled water trickles over, where bacteria on the surfaces clean it — often added after a septic tank.
Learn more → Treats the wasteReed bed
Constructed wetland
A planted gravel bed where reeds and the life around their roots polish the water — low-energy, with a wildlife benefit.
Learn more →Not sure what you've got? The signs above — and a look at any paperwork from when the property was bought or the system installed — usually tell you. If in doubt, a drainage engineer or your emptying contractor can identify it.