I'm not sure if this is the best place for this question -- please move, if necessary.
We have a seasonal pool, filled every year with well water. The well water has iron in it (don't remember levels, as it's been years since we had a water test done). We've never done anything about the iron, and never have trouble with discolored water in the pool. What happens, by dumb luck apparently, is that the iron does come out of the new fill water when we chlorinate, but the precipitate (if that's what it is) is big enough to be caught by the cartridge filters we've been using. That's been true even of the el cheapo filters we picked up at Walmart last year. So, for two weeks or so, at the start of the season, the cartridges are totally rust brown whenever I pull them out and hose them off. After that, no more rust color for the rest of the summer.
So, on to my question -
we're thinking of switching to a sand filter next year (existing cartridge filter is very much undersized for the pool, as is common knowledge here) -- since the sand is a coarser filtration medium, is it less likely to catch the iron compound and take it out of the water than the current cartridge filter? Or will the overall better filtration (larger filter) somehow make up for this?
Does anyone know what the iron precipitate is likely to be, chemically, seeing that it is large enough to be captured by the cartridge filter?