Micron rating is only one variable
A micron is a unit of particle size. Lower-number filters are finer, but choosing the smallest number available is not automatically better for a whole-house system. Heavy sediment loading can plug a fine cartridge quickly and reduce household flow.
Start with what you actually have
Visible sand or grit, rusty particulate, cloudy water and frequent cartridge fouling are useful clues, but they are not a substitute for identifying the source. Private wells may need source-specific evaluation, while municipal water problems can sometimes be related to distribution work or household plumbing.
Nominal and absolute ratings are not identical
Manufacturers may describe filters with nominal or absolute ratings, and those terms describe different capture-performance conventions. Compare the exact manufacturer's definition rather than assuming every “5 micron” cartridge performs identically.
Use staged filtration when appropriate
Where sediment load is high, a coarser first stage can protect a finer downstream stage. The correct arrangement depends on particle load, desired flow, housing size and maintenance tolerance. A pressure gauge before and after filtration can also make pressure-drop changes easier to observe.
Whole-house buying checklist
- Identify the sediment source when possible.
- Check the filter's rated flow at an acceptable pressure drop.
- Compare nominal vs absolute rating language.
- Confirm cartridge size, replacement cost and expected life.
- Provide bypass/isolation and follow local plumbing requirements.
If sediment is only one part of the problem, return to the main planner before deciding the rest of the treatment train.