Two hundred microns is coarse enough that people question whether it filters anything at all. It does, and its job is specific: catching the material that damages mechanical parts and blinds finer elements, while imposing almost no restriction on flow. Used as a first stage it makes everything behind it last longer, and used as the only stage it will disappoint.
What it stops
Sand, coarse grit, rust flakes, pipe scale, insects, and the debris that appears after work on a main or a well. Those are exactly the particles that score pump impellers, jam solenoid valves, wear valve seats and blind a fine cartridge in days. What passes straight through is fine silt, anything that makes water look hazy, and everything dissolved. So a coarse screen protects hardware and does nothing for clarity, taste or safety.
Screens rather than cartridges
At this rating the usual format is a reusable stainless or polymer screen in a clear housing, or a spin down separator with a flush valve at the bottom. Neither is a consumable: the screen is rinsed and refitted, or the housing is flushed by opening a valve, so there is nothing to buy repeatedly. That is much of the attraction on a well carrying sand. Cartridge style elements exist at coarse ratings too, but a washable screen is the sensible choice where the load is heavy.
Where it goes
First, ahead of everything. Before a pressure tank where the design allows, and certainly before any pump, cartridge filter, softener, media vessel or ultraviolet chamber, all of which are damaged or blinded by grit. On an irrigation line it protects emitters, and there the emitter orifice sets the rating rather than any drinking water consideration. Fit isolation valves either side and route the flush somewhere that can take grit, not into a septic system.
Reading what it collects
A coarse screen is also a diagnostic, because you can see what the water is carrying. A screen that needs flushing weekly on a well is telling you about the well rather than about filtration: a failed or wrongly sized screen downhole, a pump set too low, or a deteriorating formation, all of which are fixed at the well and not at the house. A screen that stays clean for months on a municipal supply and suddenly fills usually follows work on the main. Our whole house filter guide covers the finer stages behind it.
Questions people ask about 200 micron filter
Is 200 microns too coarse to be useful?
Not as a first stage. It catches the particles that damage pumps and valves and blind fine cartridges, with almost no flow restriction.
Will it make hazy water clear?
No. Fine suspended material passes straight through at that rating. Clarity needs a much finer element behind it.
Do I have to buy replacement cartridges?
Usually not. At this rating the format is a washable screen or a flushable spin down separator rather than a consumable.
My screen fills up every week. What does that mean?
On a well, that points at the well itself: a failed downhole screen, a pump set too low or a deteriorating formation.