Do I Need a Pool Filter? The Turnover Test for Home Pools

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Do I need a pool filter? Yes, for any pool that keeps its water. NSW Health says effective filtration is necessary for effective disinfection, and WA Health says a home pool’s filter should process all the water within 6 to 8 hours. For a 50,000-litre pool that means about 104 to 139 litres a minute through the filter.

The short answer

Chlorine does not remove particles; the filter does. NSW Health’s 2026 guidelines: effective filtration is necessary for effective disinfection. WA Health: filtration and disinfection are the keys.
The turnover test: pool litres ÷ (hours × 60) = litres a minute. A 50,000-litre pool needs 104 L/min to turn over in 8 hours and 139 L/min in 6.
The standard for private pools, AS 3633, quoted in one pump maker’s manual, asks for at least a single turnover of the full volume in the period the pump normally runs.
Check the filter’s maximum flow: one maker’s 22-inch sand filter is rated at 228 L/min for pools up to 60,000 litres; another’s range runs 250–400 L/min. A pump that pushes more than that shortens filter cycles.
Some germs are too tough for chlorine alone: NSW Health says Cryptosporidium is 4–6 microns and highly chlorine resistant, which is why public pools are told to filter it out.

The turnover test: litres a minute your filter must pass to turn the pool over in each target time, for 30,000, 50,000 and 70,000-litre pools (pool litres ÷ hours ÷ 60; targets from WA Health and NSW Health; filter ratings maker-published; read 14 October 2026)
Turnover target	Where the target comes from	30,000-litre pool	50,000-litre pool	70,000-litre pool
8 hours	Top of WA Health’s 6–8 hour range for home pools; one sand filter maker rates its range by an 8-hour turnover	62 L/min	104 L/min	146 L/min
6 hours	Bottom of WA Health’s range; also NSW Health’s maximum for a residential apartment pool	83 L/min	139 L/min	194 L/min
2.9 hours	NSW Health’s public-pool formula for an outdoor pool with a sand-type filter, 1.5 m average depth: (1.8 × 1.5) + 0.2	172 L/min	287 L/min	402 L/min
Filter ratings to compare against	Maker-published maximum flow	22-inch sand filter: 228 L/min, pools up to 60,000 L	Another maker’s sand range: 250–400 L/min	Cartridge: the rated flow is on the filter’s label or manual

Do I need a pool filter if I use chlorine or a salt chlorinator?

Yes. Chlorine kills microorganisms; it does not remove dirt, dead algae, sunscreen or the particles that make water cloudy. WA Health says good filtration rids a pool of dirt, debris and suspended material, and that filtration and disinfection together are what make a pool safe. NSW Health’s 2026 guidelines say effective filtration is necessary for effective disinfection.

There is also a germ chlorine struggles with. NSW Health describes Cryptosporidium as 4–6 microns, highly chlorine resistant and able to persist in pool water for days, which is why public pools are told to use filters that can remove particles of 4 microns. Those are public-pool rules, but the reason behind them is the same in a backyard.

The quotable line: a pool filter removes what chlorine cannot: particles, cloudiness and the chlorine-resistant germs that hide in them. If the water is already cloudy, start with why your pool is cloudy.

How big a pool filter do I need? The turnover test

Size a filter from the turnover you want, in three steps:

1. Pick a turnover time. WA Health says a home pool’s filter should filter all the water within 6 to 8 hours. The private-pool standard AS 3633, as quoted in one pump maker’s manual, asks for at least one turnover of the full volume in the time the pump normally runs.
2. Convert to litres a minute. Pool litres ÷ (hours × 60). A 50,000-litre pool needs about 104 L/min for 8 hours, 139 L/min for 6.
3. Check the filter’s rated maximum flow. It must be at least that figure, and at least what your pump delivers. One maker rates its 22-inch sand filter at 228 L/min for pools up to 60,000 litres; another lists 250, 320, 350 and 400 L/min across its range, with 8-hour turnover capacities of 120,000 to 192,000 litres.

For comparison, NSW Health’s formula for an outdoor public pool with a sand-type filter, (1.8 × depth) + 0.2 hours, gives 2.9 hours at 1.5 m deep, and it caps a residential apartment pool at 6 hours. Those are public-pool numbers; a family pool with a few swimmers is not held to them, but they show which way to err on a busy summer.

The quotable rule: a pool filter must pass the pool’s volume in 6 to 8 hours; for a 50,000-litre pool that is about 104 to 139 litres a minute.

What happens if the pump is too big for the filter?

The filter fails early and filters worse. One cartridge filter maker’s troubleshooting table lists short filter cycles where pump output exceeds the filter’s design flow rate. A sand filter maker’s manual lists sand coming out of the waste line, and a flow rate too high for the filter size and pool, among its faults.

So match the two. The pump’s flow at your pipework, not its brochure maximum, should sit at or below the filter’s rated flow. Energy.gov.au’s advice to choose the smallest pump size effective for your pool points the same way, and the rules on suction outlets that come with the pump are on pool pump and filter suction rules.

Sand, glass and cartridge filters all pass this test if they are sized to it. How long each lasts and what the media costs to change are on how long a pool filter lasts and what it costs to replace a pool filter.

Do I need a pool skimmer and a pool vacuum as well?

A skimmer, yes, on a permanent pool. One sand filter maker’s manual says all pools must have the appropriate fixed skimmer box: it is where the pump draws surface water and floating leaves before they sink. Its basket and the pump’s basket are the first things to empty when flow drops, and energy.gov.au lists cleaning both among the ways to cut what the pump has to do.

A vacuum or automatic cleaner is a convenience, not a health requirement: the filter cleans the water, the cleaner picks up what settles on the floor. Which type suits a pool, and what each costs to run, is a separate choice; if an existing one has stopped, see why a pool cleaner stops moving.

On a new pool, the filter model and its rated flow belong in the equipment line of every quote. Ask for them, then compare pool quotes.

Common questions

Do I need a pool filter?

Yes, for any pool that keeps its water. WA Health says filtration and disinfection are the keys to safe swimming, and that the filter should process all pool water within 6 to 8 hours.

Can I have a pool without a filter if I use chlorine?

Not safely. NSW Health says effective filtration is necessary for effective disinfection, and that Cryptosporidium is highly chlorine resistant.

What size pool filter do I need?

Divide your pool’s litres by the turnover hours times 60. A 50,000-litre pool needs about 104 L/min for an 8-hour turnover and 139 L/min for 6. Pick a filter rated above that and above your pump’s flow.

How long should a pool filter run each day?

Long enough to filter all the water once: WA Health says within 6 to 8 hours, and to keep it running at least an hour after the last swimmer gets out.

Do I need a pool skimmer?

On a permanent pool, yes. One sand filter maker’s manual says all pools must have a fixed skimmer box; it is where the pump draws surface water and floating debris.

Sources

General information only, current at 2026-10-14. Pool rules differ by state and by council, and penalty amounts are updated regularly. Confirm your own obligations with your council or a registered inspector before acting.