Which Filter Do You Have?
Almost every Aussie backyard pool uses one of three:
- Cartridge — a concertina of pleated fabric inside a tank. Most common on smaller pools and swim spas.
- Sand — a tank filled with filter sand (or glass media). Very common on mid-size concrete and fibreglass pools.
- DE (diatomaceous earth) — the finest filtration of the three. Grids inside a tank coated with DE powder.
If you're not sure, look at the tank. A big round tank with a multiport valve on top is sand or DE. A tank you open with a clamp or lid and pull a white cylinder out of is cartridge.
Cleaning a Cartridge Filter
- Turn the pump off at the wall. Close any valves if you have them.
- Release the air from the tank, undo the clamp or lid, and lift the cartridge out.
- Hose it down with a garden nozzle, working top to bottom between the pleats. Don't use a pressure washer — it tears the fabric.
- If it's greasy (sunscreen, body oils), soak it overnight in a cartridge cleaner or a bucket of warm water with a little TSP or filter-cleaner solution.
- Rinse until the water runs clear. Let it dry in the shade, then refit. Don't run a bone-dry cartridge if you can help it — a light rinse first is kinder.
Pro tip: Keep a spare cartridge. Swap them, clean the dirty one at your leisure, and you never have the pool down for half a day.
Cleaning a Sand Filter
You don't pull the sand out every time. Weekly (or when the pressure gauge is 50–70 kPa above its clean reading) you backwash:
- Turn the pump off.
- Set the multiport valve to BACKWASH.
- Turn the pump on. Run until the sight glass runs clear — usually 2–3 minutes.
- Pump off. Set valve to RINSE. Pump on for 30–60 seconds.
- Pump off. Set valve back to FILTER. Restart.
Once or twice a year, add a sand-filter cleaner through the skimmer and let it soak overnight before a long backwash. Replace the sand every 5–7 years (glass media lasts longer).
Never change the multiport valve while the pump is running. You'll chew the spider gasket and the valve will leak between ports. Pump off, then turn.
Cleaning a DE Filter
Backwash the same way as a sand filter when pressure rises. After backwashing you must recharge with DE powder — usually 1–2 kg depending on the tank size, mixed into a slurry and poured slowly into the skimmer with the pump running.
Once a year, pull the grid assembly out, hose the grids, inspect for tears, and reassemble. A torn grid dumps DE back into the pool as a fine white dust — that's your sign to replace it.
How Often to Clean
| Filter type | Summer | Winter | After a green pool |
|---|---|---|---|
| Cartridge | Every 2–4 weeks | Every 6–8 weeks | Every day until clear |
| Sand (backwash) | Weekly, or +50–70 kPa | Fortnightly | Every 4–6 hours |
| DE (backwash + recharge) | When pressure rises | As needed | Every few hours |
When to Replace It
- Cartridge: when the pleats stay flat, the fabric is torn, or pressure never drops after a clean. Typical life 1–3 years.
- Sand: when backwashing doesn't drop the pressure, or the water stays cloudy. 5–7 years for sand, longer for glass.
- DE grids: when they tear, warp, or keep dumping powder into the pool.
