Sediment Filter Micron Ratings
Volume I · May 2026 · 361 words
The micron rating of a sediment filter — the size of the smallest particle it captures — determines both the filtration quality and the frequency of filter changes. A 1-micron filter captures particles invisible to the naked eye but may clog in weeks on a high-sediment well supply; a 50-micron filter lasts months on the same water but passes particles large enough to be visible as turbidity. The correct rating balances filtration goals against maintenance frequency.
50-micron filters capture sand, silt, and rust particles visible to the naked eye (human hair is approximately 70 microns for reference). These are used as first-stage pre-filters to protect downstream equipment — water softeners, UV systems, RO membranes — from large particulate damage. The Rusco spin-down filter with a 30–50 micron screen is a reusable pre-filter that can be flushed clean without cartridge replacement.
20-micron filters capture fine sediment and are the most common whole-house filter rating, balancing adequate particle capture with acceptable pressure drop and filter life. A 20-micron pleated filter lasts 3–6 months on municipal water and 1–3 months on well water with moderate sediment.
5-micron filters capture most suspended solids and are the standard pre-filter for UV systems and RO membranes. At 5 microns, the filter removes particles that would scatter UV light and shield microorganisms from disinfection. The trade-off is faster loading: a 5-micron filter may require replacement every 1–2 months on well water.
1-micron filters approach the filtration of a sub-micron carbon block but with higher flow capacity. They capture cysts (Giardia, Cryptosporidium) which are 3–7 microns in size, providing a mechanical barrier to these pathogens. A 1-micron absolute-rated filter (guaranteed to capture 99.9% of particles at the rated size) is the functional minimum for cyst reduction without chemical disinfection. The pressure drop across a 1-micron filter is 2–3× that of a 20-micron filter of the same dimensions, requiring more frequent replacement to maintain flow rate.