This guide contains Amazon links. As an Amazon Associate, Backyard Pool Tips earns from qualifying purchases — see our affiliate disclosure. Recommendations are based on suitability and running cost, not commission.
The three filter types, honestly compared
Every residential pool filter is one of three types, and each represents a genuinely different trade-off between how fine the filtration is, how much hands-on maintenance it needs, and what it costs to keep running. There's no universally "best" one — the right choice depends on which of those three factors matters most to you.
- Sand filters
- Water passes through a bed of specially graded sand, which traps debris down to around 20–40 microns. Lowest maintenance of the three — backwash periodically, replace the sand every 5–7 years — and the cheapest to run long-term since there's no recurring cartridge or DE cost. The trade-off is the least fine filtration of the three types.
- Cartridge filters
- Water passes through a pleated fabric cartridge that traps debris down to around 10–20 microns — finer than sand. No backwashing needed (which also saves water), just periodic rinsing and eventual cartridge replacement. Generally considered the best balance of the three for most residential owners.
- DE (diatomaceous earth) filters
- Water passes through grids coated in DE powder — a fine, naturally occurring mineral — trapping particles down to as small as 2–5 microns, noticeably finer than either alternative. This gives the clearest water of the three types, but DE filters need the most hands-on maintenance: backwashing plus recharging fresh DE powder after each one, and the powder itself is an ongoing cost.
Which one actually suits your situation
- Want the lowest ongoing cost and least fuss — sand is the simplest, cheapest long-term option, and perfectly adequate water clarity for most pools.
- Want the best all-round balance — cartridge filters suit the majority of residential owners: finer filtration than sand, less hands-on work than DE, no backwashing.
- Want the clearest possible water and don't mind extra maintenance — DE gives genuinely superior clarity, chosen by owners (and some pool professionals) who prioritize water quality above convenience.
- Water-conscious or in a drought-restricted area — cartridge filters don't require backwashing at all, unlike sand or DE, which both waste water each time they're cleaned.
What each one actually costs to run
- Sand filter running cost
- Lowest of the three — sand media itself is inexpensive and lasts 5–7 years before replacement, with no recurring consumable cost between backwashes.
- Cartridge filter running cost
- Moderate — cartridges themselves cost more upfront than a bag of sand, and typically need replacing every 1–2 years depending on pool use and how consistently they're rinsed in between.
- DE filter running cost
- Highest — DE powder is a genuine recurring cost added after every backwash, on top of the filter grids themselves eventually needing replacement.
- Water cost (backwashing)
- Sand and DE filters both use a meaningful amount of water each time they're backwashed — worth factoring in for owners in water-restricted regions, where cartridge's no-backwash design becomes a real practical advantage rather than just a convenience.
Sizing a filter correctly
A filter has to be matched to your pump's flow rate (measured in gallons per minute) and your pool's total volume — an undersized filter can't keep up with the water being pushed through it, reducing filtration quality and shortening the filter's working life from constant strain. As a rough baseline, a filter should be able to turn over the pool's entire water volume at least once every 8 hours. Check both your pump's actual GPM output and the filter's rated flow capacity before buying — a mismatch between the two, in either direction, undersells what you're paying for.
Micron ratings: what they actually mean in practice
Micron rating measures the smallest particle size a filter reliably traps — a lower number means finer filtration. It's tempting to assume the finest possible filtration is always best, but there are real trade-offs worth understanding rather than just chasing the lowest number available.
- Why finer isn't automatically better
- A finer filter (like DE) restricts flow more than a coarser one at the same pressure, meaning it needs more frequent cleaning to maintain adequate flow rate — the filtration-quality gain comes with a real maintenance-frequency cost, not just a purchase-price one.
- What sand actually misses
- Sand's coarser 20–40 micron range lets some very fine particles pass through that a cartridge or DE filter would catch — in practice this rarely causes a visible clarity problem for most pools, but it's the honest reason sand is sometimes described as giving "good" rather than "excellent" water clarity.
- When the difference actually shows
- The gap between filter types is most noticeable in pools with heavy bather load, nearby dust or pollen, or an ongoing algae or clarity issue — a lightly used, well-maintained pool often looks equally clear regardless of which filter type is behind it.
Filter media technology worth knowing about
A few developments in filter media are worth understanding before buying, since they change the maintenance and performance profile of an otherwise standard filter type.
Glass media as a sand alternative
Some sand filter systems now use crushed recycled glass instead of traditional sand — it filters slightly finer, needs backwashing less often, and lasts longer before replacement. Costs more upfront than standard sand but can work out cheaper over several years given the reduced replacement frequency.
Reusable DE alternative cartridges
Some cartridge products are designed to approximate DE-level filtration without needing loose DE powder at all, aiming to combine cartridge convenience with finer filtration. Performance varies by brand — worth reading recent, specific reviews for a given product rather than assuming all "DE-alternative" cartridges perform identically.
Antimicrobial-treated cartridge material
Some cartridge filters now use fabric treated to resist mold and bacterial growth within the cartridge itself, extending the interval between deep cleanings. A genuine incremental improvement rather than a reason to skip regular rinsing altogether.
Signs your current filter needs attention
Filter pressure gauge reading high
Pressure rising 8–10 psi above your clean baseline reading means the filter media has caught enough debris to restrict flow — time to backwash (sand/DE) or clean/replace the cartridge. This is expected, normal filter behavior, not a fault. If the gauge isn't reading at all or never seems to change, see our pressure gauge troubleshooting guide.
Cloudy water despite balanced chemistry
If chemistry tests fine but the pool still looks dull or hazy, the filter itself is often the actual bottleneck — either overdue for cleaning, undersized for the pool, or (for cartridges) worn out and no longer trapping fine particles effectively. See our cloudy water guide for the full diagnostic order.
Sand or DE media past its working life
Sand filter media compacts and loses effectiveness over years of use even with regular backwashing — if pressure keeps climbing fast after cleaning despite everything else checking out, aging media is a likely cause. Sand typically needs replacing every 5–7 years, DE grids somewhat less often with proper care.
How backwashing actually works
Backwashing (used for sand and DE filters, not cartridge) reverses normal water flow through the filter to flush trapped debris out through a waste line, rather than back into the pool. Getting the sequence right matters — doing it out of order can push debris back into the pool instead of out the waste line.
-
Turn off the pump first
Never move a multiport valve or push-pull valve while the pump is running — this can damage the valve internals, which is one of the more expensive filter repairs to fix.
-
Set the valve to backwash
This reverses flow direction through the filter and routes it out to the designated waste line instead of back to the pool.
-
Run until the sight glass runs clear
Most systems have a clear sight glass in the waste line — run backwash mode until water passing through it looks clear rather than cloudy, typically 2–3 minutes.
-
Rinse for 30-60 seconds
A separate "rinse" valve setting resettles the filter media properly before returning to normal filtration — skipping this step can send a cloud of fine debris back into the pool the moment normal filtering resumes.
-
Return to filter mode
For a DE filter specifically, this is also the point to recharge with fresh DE powder through the skimmer, per your filter's rated DE capacity.
Cartridge filters skip this whole process — instead, the cartridge is removed, hosed down (or soaked in a cartridge cleaner solution for a deeper periodic clean), and reinstalled. This is the main hands-on maintenance trade-off between the filter types discussed above.
Mistakes that shorten a filter's working life
Backwashing on a schedule instead of by pressure
Backwashing too often wastes water and can actually reduce filtration quality — sand and DE media both filter better once they've built up a light layer of trapped debris. Go by the 8–10 psi pressure rise rule rather than a fixed calendar schedule.
Letting a cartridge go too long between cleanings
A heavily clogged cartridge restricts flow, forcing the pump to work harder and reducing turnover — by the time it's visibly gray or won't rinse clean, it's often overdue by weeks, not days.
Ignoring persistent high pressure after cleaning
If pressure stays high immediately after backwashing or cleaning, the media itself may be worn out (compacted sand, degraded cartridge pleats) rather than simply dirty — see our pump and filter troubleshooting guide for the full diagnostic path.
Mismatching filter size to pump output
A filter rated below your pump's actual flow rate gets pushed harder than intended, shortening media life and reducing filtration quality — always check both figures together when replacing either the pump or the filter, not just the one you're buying.
Environmental and water-use considerations
Filter choice has a real environmental footprint beyond just the filter itself, worth weighing alongside performance and cost — particularly for owners in drought-prone or water-restricted regions.
- Backwash water use
- Sand and DE filters both discharge a meaningful volume of water to waste with every backwash — depending on backwash frequency and local water cost, this adds up over a season and is a genuine, often-overlooked factor in some regions' water restrictions specifically targeting pool backwashing during drought periods.
- DE powder disposal
- Spent DE powder from backwashing needs to be disposed of according to local regulations rather than simply washed to a storm drain, since it can affect local waterways — check municipal guidance, as rules vary meaningfully by location and some areas require it be swept up and bagged rather than backwashed to waste at all.
- Cartridge waste
- A used cartridge is a solid waste item replaced every 1–2 years rather than an ongoing water-use concern — some manufacturers and specialty retailers offer recycling programs for old cartridges, worth checking before simply discarding one.
- Recapture systems
- Some owners in water-restricted areas install a backwash recapture system that settles out debris and allows water to be reused rather than sent entirely to waste — a bigger upfront investment, but worth investigating for a sand or DE filter in a region where water cost or restriction is a real constraint.
Five filters worth considering
Spanning cartridge, sand, and DE across budget and premium options.
Pentair Clean and Clear Plus 420 Cartridge Filter
Cartridge filter · Pentair
Strengths
- Strong flow capacity for mid-to-large inground pools
- No backwashing needed — easy maintenance and water-efficient
Trade-offs
- Replacement cartridges cost more than sand filter media over the same period
Best for: most inground pool owners wanting the best balance of filtration and low-effort maintenance.
Check current price on Amazon →Hayward Star Clear Plus C900 Cartridge Filter
Cartridge filter · Hayward
Strengths
- Widely available parts and cartridges given Hayward's market share
- Reliable filtration for standard residential inground pools
Trade-offs
- Comparable performance to the Pentair option — comes down to brand/parts preference
Best for: owners who already run Hayward equipment and want matching parts availability.
Check current price on Amazon →INTEX Krystal Clear Sand Filter Pump 3000 GPH
Sand filter + pump combo · INTEX
Strengths
- Combined filter and pump unit — simple, affordable above-ground setup
- Automatic timer and low ongoing running cost
Trade-offs
- Sized for above-ground pools up to around 16,000 gallons — not suited to larger inground pools
Best for: above-ground pool owners wanting the simplest, cheapest complete filtration setup.
Check current price on Amazon →Hayward Pro Series S180T Sand Filter
Sand filter · Hayward
Strengths
- Low ongoing cost and minimal maintenance for a standard inground pool
- Durable tank construction backed by an established brand
Trade-offs
- Requires a separate pump — not a combined unit like the INTEX option
- Coarser filtration than cartridge or DE
Best for: inground pool owners prioritizing lowest long-term running cost over the finest filtration.
Check current price on Amazon →Pentair FNS Plus DE Filter
DE filter · Pentair
Strengths
- Traps particles far finer than sand or cartridge, giving noticeably clearer water
- Established, well-regarded DE filter line
Trade-offs
- Highest maintenance effort and running cost of the three filter types
- Requires careful DE powder handling and backwash disposal per local regulations
Best for: owners prioritizing the clearest possible water and comfortable with the extra maintenance.
Check current price on Amazon →New pool vs replacing an existing filter
The buying decision looks a little different depending on which situation you're in, and it's worth being clear about which one applies before choosing a product.
New pool, no existing equipment
You have a genuinely open choice between all three filter types — this is the point to weigh maintenance effort, running cost, and filtration quality against each other without the constraint of matching existing plumbing or a pump that's already sized for a specific filter type.
Replacing a failed or worn-out filter, same type
The simplest replacement path — matching your existing filter type and flow rating avoids re-plumbing and keeps the swap straightforward, usually a same-day job for anyone reasonably comfortable with basic pool equipment work.
Switching filter types on an existing pool
Possible, but budget for re-plumbing work around the filter tank connections, and double check your existing pump's flow rate suits the new filter type's requirements — a pump sized well for a sand filter isn't automatically well-matched to a DE filter's different flow characteristics.
Our verdict by scenario
- Best all-round choice
- The Pentair Clean and Clear Plus 420 balances filtration and easy maintenance well.
- Already running Hayward equipment
- The Hayward Star Clear Plus C900 keeps parts and service consistent.
- Above-ground pool, simplest setup
- The INTEX Krystal Clear combined sand filter and pump is hard to beat for ease.
- Inground pool, lowest running cost
- The Hayward S180T sand filter keeps ongoing costs to a minimum.
- Want the clearest water possible
- The Pentair FNS Plus DE filter delivers the finest filtration of this list.
Common questions
Which filter type is actually best?
DE filters catch the finest particles and give the clearest water, cartridge filters offer the best balance of filtration quality and easy maintenance, and sand filters are the lowest-effort and cheapest to run. There's no single best filter — it's a genuine trade-off between filtration fineness, maintenance effort, and running cost.
How often should I clean or replace my filter?
Cartridge filters need rinsing every 2–4 weeks and full replacement every 1–2 years. Sand filters get backwashed when pressure rises 8–10 psi above clean baseline, roughly every 4–6 weeks, with sand media replaced every 5–7 years. DE filters get backwashed similarly to sand, with fresh DE powder recharged after every backwash.
Can I switch from sand to cartridge, or between filter types?
Generally yes if the new filter is correctly sized for your pump's flow rate, though it usually means replacing the whole filter tank rather than converting an existing one — the internal design differs enough between types that conversion kits are rare and situational.
Why is my filter pressure gauge reading high?
Rising pressure above your clean baseline means the filter media is catching debris and needs cleaning or backwashing — this is normal filter behavior, not a fault. Our pump and filter troubleshooting guide covers what to do if pressure stays high even right after cleaning.