Pool & Spa Filter Cartridges: Sizing Guide & Replacements

Pool filter cartridges are measured by three critical dimensions: outer diameter, inner diameter, and length. Even a half-inch discrepancy in any measurement will cause water bypass — unfiltered water flowing around the cartridge rather than through it. Always measure your existing cartridge or reference the filter housing model number.

The square footage rating of your filter cartridge must match or exceed your pool's volume. For residential pools up to 15,000 gallons, a 100-200 sq ft cartridge is standard. For pools up to 30,000 gallons, look for 200-400 sq ft ratings. Undersizing your filter leads to rapid clogging and poor circulation.

Compatible pool filter cartridges use identical pleated polyester media to OEM versions. The pleat count, media thickness, and end-cap sealing are manufactured to the same tolerances. The only difference is the brand name printed on the label — and the price, which is typically 40-60% lower.