Pool Filter Buying Guide: Sand vs. Cartridge vs. DE
Sand, cartridge, or DE? Learn which pool filter is right for your pool, how to size it correctly, when to replace your cartridge, and shop replacement filters.
Poolzilla Buying Guide
Pool Filter Buying Guide:
Sand vs. Cartridge vs. DE
Your filter is quietly the most important equipment decision you'll make. Get it wrong and you'll spend years fighting cloudy water, wasted chemicals, and frustrating maintenance. Here's everything you need to choose correctly.
Start Here
Which Filter Is Right for You?
Not sure where to start? Pick the description that fits, then read that section in full.
Sand Filter
You want low hands-on maintenance, have a large inground pool, and are okay with "good enough" clarity. Or you want the cheapest entry point.
Easiest MaintenanceCartridge Filter
You have an above ground pool, want noticeably cleaner water than sand, no backwashing, and straightforward hose-off maintenance.
Most PopularDE Filter
You want the absolute finest water clarity available, have an inground pool, and you're comfortable with a more involved maintenance routine.
Best ClarityAbove Ground Pool? Almost Always Cartridge.
Cartridge filters dominate the above ground pool market because they're compact, require no backwash valve or multiport plumbing, produce excellent water clarity, and are dead simple to maintain. Poolzilla stocks replacement cartridges for the most popular above ground filter systems โ so when yours wears out, you're covered. More on this below.
Before We Go Deep
Understanding Microns: The One Number That Matters
Every filter comparison leads back to microns โ the unit of measurement that tells you how small a particle the filter can actually catch. One micron = one millionth of a meter. A strand of human hair is about 70 microns wide. To give you perspective on what these filters are doing:
Filtration Rating by Filter Type (smaller = better)
For reference: most bacteria range from 2โ15 microns. Algae spores: 10โ30 microns. Pollen: 10โ100 microns. Sand filters miss a lot; DE catches nearly everything. Cartridge hits the practical sweet spot for most residential pools.
One important nuance most guides skip: a clean sand filter actually performs at its worst โ filtering only down to ~40 microns. As the sand bed loads with debris, filtration improves to ~20 microns. This means sand filter performance is variable and degrades as the sand erodes over years. Cartridge and DE filters maintain more consistent performance throughout their service life.
Microns Aren't the Whole Story
Micron ratings are "nominal" โ meaning they describe what the filter captures at typical conditions. Real-world filtration also depends on flow rate (too fast = poor filtration), filter condition, and water chemistry. A properly sized filter running at the right flow rate will always outperform an undersized one regardless of micron rating. More on sizing below.
Filter Type 01
Sand Filters
Sand filters have been the dominant pool filter type for decades, and with good reason โ they're rugged, inexpensive, and genuinely low-effort to maintain. The tradeoff is filtration quality: of the three types, sand filters let the most through. For most large inground pools they're perfectly adequate, but they're not the right call for every situation.
โ Pros
- Lowest day-to-day maintenance burden
- Sand media lasts 7โ10 years before replacement
- Lowest upfront equipment cost
- Handles high water volumes well โ great for large pools
- Simple, time-proven technology โ very little to break
- Backwashing takes 2โ3 minutes
โ Cons
- Worst filtration quality of the three types
- Misses algae spores, fine pollen, sunscreen particles
- Backwashing wastes 250โ300 gallons per cycle
- Backwash can throw off your water chemistry balance
- Sand erodes over time, reducing effectiveness
- Spring opening and algae recovery can take 1โ2 weeks
- Requires multiport valve โ more plumbing complexity
Filter Type 02
Cartridge Filters
Cartridge filters are the dominant choice for above ground pools and the fastest-growing filter type overall. They filter twice as fine as sand, produce noticeably cleaner water, require no backwashing, and are the simplest filter to maintain. If you have an above ground pool, this is almost certainly what you have โ and what you should have.
Why Cartridge Wins for Above Ground Pools
Above ground pool equipment is designed to be compact, low-pressure, and simple. Cartridge filters fit perfectly: no backwash valve, no multiport plumbing, lighter and smaller than sand systems. They pair especially well with variable speed pumps โ running at lower RPM, cartridge filters actually work better, capturing finer particles at lower flow rates. Poolzilla stocks replacement cartridges for the most popular above ground filter brands. When yours wears out mid-season, you're not hunting for an obscure part โ we ship nationwide.
โ Pros
- Filters to 10โ20 microns โ significantly cleaner water than sand
- No backwashing โ saves thousands of gallons per season
- No multiport valve โ simpler plumbing and installation
- Compact and lightweight โ ideal for above ground setups
- Lowest upfront cost of the three types
- Saltwater pool compatible
- Works best at lower flow rates โ pairs well with variable speed pumps
- Faster algae and cloudy water recovery than sand
โ Cons
- Cartridge replacements are an ongoing cost (1โ3 years)
- Requires more frequent cleaning than sand in high-use pools
- Can clog faster during algae blooms โ requires immediate attention
- Very large inground pools may need an oversized quad-cartridge system
Filter Type 03
DE (Diatomaceous Earth) Filters
DE filters produce the finest, clearest water of any pool filter โ full stop. They filter down to 2โ5 microns, which is fine enough to catch most bacteria, algae spores, and even fine pollen that passes straight through sand and most cartridge systems. The water quality difference is genuinely visible. The tradeoff is a more involved maintenance routine and the highest upfront cost.
Handle DE Powder with Care
Diatomaceous earth is a fine silica dust. Always wear a dust mask when measuring and adding DE powder โ breathing silica dust over time is a health concern. Use pool-grade DE only (not food-grade). Also note: spent DE cannot be freely dumped in storm drains in many areas โ check your local regulations. This isn't a dealbreaker, but it's a real consideration that most guides gloss over.
โ Pros
- Finest filtration available: 2โ5 microns
- Catches algae spores, bacteria, and fine pollen other filters miss
- Spa-quality water clarity โ genuinely visible difference
- Spring opening and algae recovery can happen in 1โ2 days vs. weeks
- Preferred filter type for commercial pools and serious pool owners
- Filter grids last 7โ10 years
โ Cons
- Highest upfront cost of the three types
- Must add fresh DE powder after every backwash โ extra step, ongoing cost
- DE powder requires careful handling (dust mask) and proper disposal
- Full grid teardown required 1โ2x per year
- Torn grids allow DE into pool โ inspect annually
- Not practical for above ground pools
- More complex system โ steeper learning curve for first-time owners
Side-by-Side
Full Comparison Table
Every spec that matters, in one place. Green = best in category.
| Factor | ๐ชฃ Sand | ๐ต Cartridge | ๐ฌ DE |
|---|---|---|---|
| Filtration Fineness | 20โ40 microns | 10โ20 microns | 2โ5 microns |
| Water Clarity | Good | Very Good | Excellent |
| Catches Algae Spores? | Partially | Mostly | Yes โ reliably |
| Upfront Equipment Cost | $$ | $ | $$$ |
| Ongoing Operating Cost | Very Low | Low (cartridge replacement) | Moderate (DE powder + grids) |
| Ease of Maintenance | โ โ โ โ โ | โ โ โ โ โ | โ โ โ โโ |
| Water Usage (Backwash) | 250โ300 gal per cycle | None | 250โ300 gal per cycle |
| Best for Above Ground? | Acceptable | Yes โ ideal | No |
| Best for Large Inground? | Yes | Yes (oversize if needed) | Yes โ premium |
| Saltwater Pool Compatible | With glass/zeolite media | Yes | Yes |
| Works with Variable Speed Pump | Yes | Yes โ optimal pairing | Yes |
| Algae/Spring Recovery Time | Up to 1โ2 weeks | 2โ5 days | 1โ2 days |
| Media / Element Lifespan | 7โ10 years (sand) | 1โ3 years (cartridge) | 7โ10 years (grids) |
| DIY-Friendly? | Very easy | Very easy | Moderate complexity |
Getting the Size Right
How to Size a Filter for Your Pool
Undersizing a filter is one of the most expensive mistakes pool owners make. An undersized filter runs at high constant pressure, degrades faster, and simply can't keep up. Here's the correct approach โ the same method professional pool builders use.
Step 1: Know your pool volume. You need your pool's gallon capacity to size everything correctly. Use the right formula for your pool shape:
โฌ Rectangular
Average depth = (shallow + deep) รท 2. Multiply result by 7.5 to get gallons.
โญ Round
Use diameter (not radius). Multiply squared diameter by depth then by 5.9.
๐ Oval
Length ร width gives the surface area. Multiply by depth and 6.7 for gallons.
โ Irregular / Kidney
W1 and W2 are the widths at each end of the pool's widest points.
Step 2: Calculate your target flow rate (GPM). The industry standard is two full turnovers per day. One turnover removes approximately 37% of contaminants; two turnovers reaches about 86% โ the practical clean-water threshold for residential pools.
Minimum GPM Formula (2 Turnovers / Day)
Pool Volume (gallons) รท 720 = Minimum GPM Required
720 = two 6-hour filtration cycles per day. For one 8-hour cycle: use รท 480. For 24/7 operation: use รท 1,440.
Step 3: Match and oversize. Select a filter rated for at least 10โ20% more GPM than your calculation. A filter running below its maximum rated flow rate operates at lower pressure, filters more finely, and lasts significantly longer. Always buy bigger, not smaller.
Match Your Pump and Filter โ Always
A pump that pushes more GPM than your filter is rated for creates excessive pressure, damages filter media, and reduces filtration quality. The filter's maximum GPM rating must always be higher than your pump's flow rate. If you're upgrading your filter, check your pump's output. If you're upgrading your pump, check your filter's maximum rating. See our equipment and pumps collection for properly matched pump options.
Cartridge Filter Care
When to Clean vs. Replace Your Cartridge
This is the most common question we field. The answer isn't just a calendar date โ it's a performance-based decision. Here's the full picture, including a useful rule of thumb most guides miss entirely.
The Half-Life Rule โ The Best Replacement Signal
Track how many days pass between cleanings (when the PSI rises 8โ10 above baseline). When that interval drops to roughly half of what it used to be โ you used to go 3 weeks between cleanings and now it's only 10 days โ the cartridge has reached its "half-life." This is the most reliable indicator that your cartridge can no longer hold adequate debris between cleanings, and replacement will be more cost-effective than continued cleaning.
Cartridge lifespan varies significantly by use:
๐ฟ Clean It
- PSI is 8โ10 above baseline โ first sign
- It's been 2โ4 weeks since last rinse
- Return jets feel weaker than normal
- Pleats are dirty but intact and uncrushed
- No tears, cracks, or fraying visible
- After a heavy pool party or unusually busy weekend
๐ Replace It
- Pressure stays high immediately after a thorough cleaning
- Cleaning intervals are half what they used to be (half-life rule)
- Pleats are torn, frayed, collapsed, or crushed at the ends
- Dark brown, gray, or oily stains won't clean off after soaking
- End caps have cracks or visible breaks (not just stress marks)
- Pleat bands are significantly broken down, affecting spacing
- Water stays cloudy despite balanced chemistry and clean filter
Pro Move: Run Two Cartridges in Rotation
Buy two cartridges for your filter system. When one needs cleaning, swap in the clean spare so your pool keeps running uninterrupted. Then take your time with the dirty one โ a proper cleaning means removing loose debris by hand, hosing from top to bottom through the pleats, then soaking overnight in cartridge filter cleaning solution to dissolve oils. Never use a pressure washer โ it damages the polyester pleats. Rotating two cartridges extends the life of both and means you're never caught off guard mid-season.
Rinsing vs. Deep Cleaning โ Know the Difference
A garden hose rinse removes surface debris. It does not remove sunscreen oils, body oils, and mineral scale that slowly saturate the pleats. Over time, this buildup is the main reason cartridges fail prematurely. Once mid-season (or after any algae event), soak the cartridge in a dedicated cartridge cleaning solution for at least 8โ12 hours. This dissolves embedded oils and dramatically extends cartridge life. Skipping deep cleans is the single most common reason pool owners replace cartridges far too early.
Need a Replacement Cartridge?
Poolzilla stocks filter cartridges for the most popular above ground and inground filter systems. Find your model and get it shipped fast, nationwide.