Sand, cartridge, and diatomaceous earth (DE) — every pool filter uses one of these three media types. Each has distinct filtration efficiency, maintenance requirements, water usage, and lifecycle costs. Understanding the differences helps you choose the right system for new installations and recommend upgrades intelligently.
Filtration efficiency comparison
| Media Type | Particle Size (microns) | Backwash Required | Water Usage | Maintenance Frequency |
|---|---|---|---|---|
| Sand | 20–40 microns | Yes (weekly to monthly) | High (backwash) | Low |
| Cartridge | 10–15 microns | No (remove and rinse) | Low | Moderate |
| DE | 3–5 microns | Yes (backwash + recharge) | Moderate | High |
Sand filters
The most common filter type in Florida residential pools. Silica sand (grade #20) captures particles through a combination of mechanical straining and adhesion as water passes through the bed. Advantages: low maintenance, durable (sand lasts 5–7 years), and backwashing is easy. Disadvantages: lowest filtration efficiency — particles smaller than 20 microns (including some bacteria, algae spores, and fine pollen) pass through.
Upgrade option: Replace sand with ZeoSand, FilterGlass, or AFM (Activated Filter Media) to improve filtration to 10–15 microns without changing the tank or plumbing.
Cartridge filters
Cartridge filters use pleated polyester fabric elements to strain water. No backwashing — simply remove the cartridge(s) and rinse with a garden hose. Advantages: best choice for areas with water restrictions (no backwash water waste), good filtration efficiency, and simple maintenance. Disadvantages: cartridges need periodic chemical cleaning (acid soak) and replacement every 1–3 years. Cannot filter as fine as DE.
In Florida, cartridge filters are increasingly popular because many areas restrict backwash discharge to lawns and drain fields.
DE filters
Diatomaceous earth — the fossilized remains of microscopic algae (diatoms) — coats fabric grids inside the filter tank. The DE powder itself provides filtration at 3–5 microns, capturing nearly everything visible in the water. Advantages: superior water clarity, best choice for algae-prone pools. Disadvantages: highest maintenance burden, DE powder is messy, grids need annual inspection and occasional replacement, and backwash requires adding fresh DE after every cycle.
Choosing the right filter
- Heavy debris load or large pool: Sand filter with alternative media
- Water restriction area or ease of maintenance: Cartridge
- Crystal clarity priority or algae history: DE
- Commercial or high-bather-load: DE or cartridge
Filter choice matters most during algae recovery. A sand filter running at 20-micron filtration will clear a green pool much more slowly than a DE filter at 5 microns. When customers call with recurring clarity problems, the filter is often part of the answer.
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