5 Micron or 20 Micron? Here's What People Actually Get Confused About
Micron ratings sound simple until you're actually staring at a filter housing trying to decide between two numbers. Based on what people keep asking, here's the real breakdown.
🔹 Is a 5 or 10 micron filter better?
Neither is universally "better" they're catching different things. 5 micron is the standard for general drinking water pre-filtration, catching fine dust, silt, and the stuff that makes water cloudy. 10 micron is one step coarser, catching finer dirt and sediment than a 25 micron filter would, but letting more fine particulate through than a 5 micron does. If your water has genuinely fine cloudiness, go 5. If you just need general sediment control without excessive clogging, 10 works fine.
🔹 5 micron vs 20 micron: which is finer?
5 micron is finer. Fewer microns means smaller holes means smaller particles caught. 20 micron sits in the range for large dirt, sand, and rust flakes, usually used as a first-stage well water pre-filter, not a final polish. Think of 20 micron as the coarse first pass and 5 micron as the finer stage after that.
🔹 1 micron vs 5 micron: the real tradeoff
1 micron gets you into genuinely serious territory catching microscopic parasites like Giardia and Cryptosporidium. That's a meaningful jump in protection over 5 micron. But it comes with a real cost: a 1 micron filter clogs faster and reduces flow rate more than a 5 micron would, since it's blocking so much more per gallon that passes through. If you don't actually have a parasite risk in your water source, jumping straight to 1 micron just means more frequent filter changes for protection you don't need.
🔹 What's the best micron rating for well water?
Well water usually needs a staged approach rather than one filter doing everything. Start coarse 20 to 50 micron to catch sand and rust flakes that are common in well water. Then follow with something finer, often 5 micron, for the remaining fine sediment and cloudiness. Skipping the coarse first stage and jumping straight to a fine filter means that fine filter clogs almost immediately trying to catch debris it was never meant to handle alone.
🔹 Nominal vs. absolute the distinction nobody explains well
This trips people up constantly. A nominal rating means the filter catches roughly 85% of particles at that stated size most consumer filters use this. An absolute rating means it catches 99.9% of particles at that size, but costs more and clogs faster. A "5 micron" nominal filter and a "5 micron" absolute filter are not the same product, even though the number on the label looks identical. If you're comparing filters and only checking the micron number, you're missing half the actual spec.
🔹 The pattern across all these questions
There's no single "correct" micron rating that applies everywhere. It depends entirely on what's actually in your water and what you're trying to protect downstream. Getting this wrong in either direction has a real cost: too coarse and contamination gets through, too fine and you're clogging filters constantly for protection you may not even need.
If you want the full breakdown including the complete range from 50 microns down to 0.035 microns and how nominal vs. absolute changes your actual filtration outcome Brother Filtration's guide on choosing water filter micron ratings covers it in more depth.