Well water carries sediment: fine sand, silt, rust flakes, and the occasional surprise from a shifting water table. Without filtration, that grit chews up pump seals, clogs fixtures, and shortens the life of every downstream appliance. Sizing the sediment filter by micron rating is how you match the filter to the grit without choking the system.
What micron ratings mean
A micron rating describes the particle size a filter catches. A 50-micron filter stops coarse sand and large rust flakes while letting fine silt through; a 5-micron filter catches most visible sediment but clogs faster. The rating is a tradeoff between protection and maintenance interval, not a race to the smallest number. Oversizing toward the fine end on the main filter alone usually just means you are changing cartridges constantly, while the right coarse-first approach lets each stage do its job.
Staged filtration: coarse, then fine
The standard approach for well mains is two stages: a coarse filter around 50 microns first, then a fine filter around 5 to 20 microns second. The coarse stage catches the big stuff that would instantly plug the fine cartridge, and the fine stage polishes the water. Each stage can be a separate housing in series, plumbed so either can be serviced without draining the system. This arrangement extends cartridge life dramatically compared to a single fine filter trying to do everything, and it keeps the pressure drop across each stage modest.
Flow rate and pressure drop
Every filter costs you some pressure, and that cost grows as the cartridge loads up. Size the filter housings for your system's peak flow, not the average; a filter that is fine at laundry-day flow may choke when the well pump hits full draw. Check the housing's flow rating and keep the pressure drop across clean cartridges low, a few pounds at most. Install pressure gauges on both sides of the filter bank so you can see the drop rising. When the drop reaches about 10 to 15 pounds above clean, it is time to change cartridges, regardless of the calendar.
Matching the rating to your water
Not all well sediment is alike. A new well that pumps a little sand for its first months needs coarse protection most; an older well with fine silt or iron sediment needs the fine stage to do more work. Look at what actually comes out: fill a glass jar from an outdoor spigot, let it settle, and inspect the sediment layer. Visible sand grains point to a coarser first stage; fine cloudy silt means the fine stage matters more. Retest after heavy rains or pump work, because wells change what they deliver.
Filter type choices
Spun polypropylene cartridges are cheap and effective for sediment but clog from the outside in and are not cleanable. Pleated cartridges hold more dirt and can sometimes be rinsed and reused a few times. String-wound cartridges handle heavier sediment loads. For the coarse first stage, a cleanable or high-capacity cartridge saves money over time; for the fine stage, a disposable spun cartridge is usually the practical choice. Match the type to how fast each stage loads up in your system.
Placement in the system
The sediment filter bank goes right after the pressure tank and before the water softener, iron filter, or anything else downstream. The pressure tank's drawdown cycle means flow through the filter is intermittent and sometimes surging, so size for the pump's full output. Put isolation valves on both sides and a bypass loop so you can service the filters without shutting down the house. A whole-house bypass is the difference between a five-minute cartridge change and a household held hostage by maintenance.
Test your water, stage coarse then fine, size for peak flow, watch the gauges, and keep a bypass for service. Done this way, the sediment filter protects the whole system quietly and asks only for a cartridge change on schedule.
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