Use coarse sediment protection before the iron filter when the well carries visible particles. Avoid very fine restrictive cartridges unless the treatment train specifically requires them.
When sediment prefiltration helps
Sand, grit and visible particulate can damage control valves or occupy media-bed space. A spin-down or coarse cartridge can remove bulk load first.
Do not choke the iron filter
A fine cartridge that clogs rapidly can starve the iron filter of service and backwash flow. Choose the coarsest stage that solves the actual particle problem.
Backwash systems already handle some suspended load
Regenerating media filters are designed to flush captured material, so not every well needs an aggressive cartridge stage upstream.
Watch differential pressure
If downstream pressure falls as the sediment filter loads, replacement should be driven by pressure behavior as well as calendar age.