If you're standing in front of a pool shop counter or reading a quote from a tradie and seeing "sand filter" on one line and "cartridge filter" on the next, you're not the first Australian homeowner to get stuck on which one to pick. Both filters do the same core job — pulling water from the pool, straining out dirt, hair, sunscreen and fine debris, then pushing clean water back through the returns — but the mechanics behind that, and what it costs you in time and water each month, differ quite a bit.
This guide breaks down how each filter actually works, how they compare on water clarity, running costs and hands-on maintenance, and which one makes more sense depending on your water source, budget and how much backwash water your council will let you send down the drain. By the end you should be able to read a filter quote and know exactly what you're paying for.
A sand filter holds a bed of graded silica sand — typically 20-40kg for an average residential tank — inside a fibreglass or steel tank. Pool water enters at the top, filters down through the sand bed, and exits through a network of laterals at the bottom. Dirt gets trapped between the sand grains, and once the tank's pressure gauge climbs about 8-10 psi above its clean starting pressure, you backwash it by reversing the flow so trapped dirt flushes out through a waste line.
A cartridge filter works differently. Water passes through one or more pleated polyester fabric elements sitting inside a plastic housing, similar to a large, reusable air filter. Dirt collects on the surface of the pleats rather than inside a sand bed, and instead of backwashing, you pull the cartridge out, hose the muck off between the pleats, and put it back in.
The practical difference that matters most to homeowners is what happens to the trapped dirt: a sand filter flushes it out with water you have to dispose of somewhere legal, while a cartridge filter just needs a hose and a spare hour, with no waste water leaving the system at all.
Cartridge filters generally catch finer debris than sand filters, trapping particles down to roughly 10-15 microns compared with a sand filter's 20-40 microns, which matters if your pool tends toward cloudy water or you're chasing glass-like clarity. A micron is one-thousandth of a millimetre, and the lower the micron rating, the smaller the particle a filter can remove before it passes back into the pool.
In practice, the gap is smaller than it sounds for a well-maintained pool. A sand filter running the right sand grade, balanced chemistry and a correctly sized pump will still produce clear water for normal residential swimming, which is why builders have installed them on suburban pools across Australia for decades without complaints. Cartridge filters tend to pull ahead in pools dealing with fine, persistent haze — dust storms inland in NSW and SA, ash during bushfire season, or heavy pollen in spring — where the finer mesh keeps stripping particles a sand bed lets slip through.
Diatomaceous earth (DE) filters sit above both, filtering to around 2-5 microns, but they're less common on new residential builds because of the DE powder handling involved and stricter disposal rules some councils apply. For most homes choosing between cartridge and sand, filtration quality alone rarely decides it; cost and maintenance time usually do.
A sand filter costs less to buy but more to run over time, mainly because backwashing wastes water and the sand itself needs replacing every 5-7 years. Each backwash cycle typically uses somewhere between 200 and 1,000 litres, depending on tank size and cycle length, and a pool with moderate bather load might need backwashing weekly through an Australian summer.
On mains water rates in most capital cities (roughly A$2-4 per kilolitre depending on the state and usage tier), the backwash water itself is a minor line item, but on tank water, or during the water restrictions some SA and regional NSW and QLD councils still apply to pool backwashing, that wasted water matters more than the dollar figure suggests.
Expect to backwash a sand filter roughly weekly through summer and monthly or less in cooler months, and to replace the sand bed every 5-7 years. Filter-grade silica sand typically costs A$25-40 a bag, and an average residential tank needs 3-4 bags, so a full sand change usually runs to A$100-200 in materials plus A$100-200 in labour if a pool tech does it rather than you doing it yourself.
A cartridge filter uses no backwash water at all — you just hose the element off in the yard every 2-4 weeks through swimming season. The trade-off is the cartridge itself, which typically needs replacing every 2-3 years and costs somewhere between A$80 and A$250 depending on size, more again for twin or quad set-ups where you're replacing several elements at once.
Skipping maintenance on either filter type leads to the same result: rising pressure, reduced flow, and a pump working harder than it should, which can shorten pump life and push up chlorine demand because water isn't circulating properly.
With a sand filter, maintenance is mostly about watching the pressure gauge and backwashing once it reads 8-10 psi above the clean baseline, then giving the multiport valve a visual check each season for worn seals, a common cause of unexplained pressure loss. With a cartridge filter, maintenance is more hands-on and more frequent but involves no valve — you're pulling the element, hosing between the pleats, and occasionally soaking it overnight in a filter-cleaner solution (roughly A$15-25 a bottle) to shift oils and scale a hose alone won't remove.
Pools with heavy bather load, such as shared pools or ones used for regular kids' parties, clog cartridges faster mid-summer, sometimes needing a clean every 1-2 weeks instead of the usual 3-4.
A pressure gauge reading 8-10 psi above its clean start point is the clearest sign a sand filter needs backwashing, while a cartridge filter usually shows itself through reduced flow at the return jets or a pump straining audibly before the gauge moves much at all. Cloudy water despite a normal pump cycle, algae returning within days of a chlorine shock, or a dropping water level near the returns are all signs the filter, not just the chemicals, needs checking.
Cleaning a cartridge or backwashing a sand filter doesn't require a licence in any Australian state, but swapping a filter housing that involves rewiring the pump or altering fixed electrical connections does. That work has to be done by an electrician licensed through the relevant state body — NSW Fair Trading, the VBA in Victoria, Building and Energy in WA, or CBS in SA — and any pool builder or tech quoting the job should be able to confirm who holds that licence.
Choose a sand filter if you want the lower upfront cost and don't mind backwashing weekly through summer; choose a cartridge filter if you're on tank water, face council water restrictions, or want to avoid a waste-water disposal problem altogether. Upfront, a sand filter system — tank, sand and multiport valve — typically costs somewhere between A$500 and A$1,200 supplied and fitted for an average residential pool, while a comparable cartridge system typically runs A$400-900; sand can be cheaper to install, but its backwash water and sand-replacement cycle add up over the years a cartridge owner spends on new elements instead.
Space and plumbing matter more than most people expect: cartridge housings generally have a smaller footprint and don't need a waste line run to a legal disposal point, which matters on tight suburban blocks where equipment sits hard against a side fence. Sand filters need that waste line plumbed to sewer, a soakwell, or garden irrigation — never straight to stormwater, since most Australian councils treat pool backwash water as trade waste or greywater and prohibit stormwater discharge because of the chlorine and salt it carries.
A cartridge filter is usually the better fit if your pool draws from tank water or your property runs on a septic system, since it doesn't waste litres on backwashing and doesn't send chlorinated water into a septic tank that isn't designed to handle it.
A sand filter generally needs less hands-on time overall — a weekly backwash takes minutes — even though it uses more water, while a cartridge filter demands more frequent physical cleaning but skips the valve mechanics and pressure-gauge routine altogether.
Cartridge vs Sand Filters: Which Is Better for Your Pool? — common questions
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