Are you perhaps having an iron bacteria problem?
I have some experience in using water that has an iron/iron bacteria problems in a commercial ornamental plant production nursery as well as for grounds use.
Of course overhead watering of retail production stock yields plants that are commercially unsightly however the water charges for council supplied water are too expensive at $2.83 per Kilo litre.
I've done extensive research on this subject and have come up with several solutions and I'm not convinced that filtration will solve your problems for iron. I'd be interested to hear about this expensive treatment system you are mentioning.
If it's bacteria,it's claimed that bores can be bombed with chlorine to cure them.
An other solution that I found,I think by a govt dept a number of years ago,was to aerate the water into a large tank and let it sit overnight for the iron to fall out of solution by the time you want to use it.This would probably be costly and impractical for your use as you'd need a large tank and a second pump with associated electrical control system.
I've managed to make my water usable by using drippers with I think about a 120 micron filter but my problem is not as sever as it can be.Another way for me to use this water,if doing overhead watering, is to say water the stock for 9 mins on borewater and then rinse for 1 min using town water.This is easy enough when it's all electrically automated after the initial installation.
As I understand it,it's very difficult if not impossible to practically filter dissolved iron from water.Aeration I think offers the best solution and if filtration is possible,depending on the amount of iron in your water,it would probably quickly clog your filter.
I've also seen a "device" that is supposed to treat water so that the iron doesn't stain by altering it so that it doesn't react with air.
It seems to have a pseudo scientific explanation how it works but I'm not convinced.
It basically is a length of stainless steel pipe about 300mm long with black box technology in between that you screw inline.
I saw that years ago at an irrigation shop now called Eden.
One solution would be to tile your bathroom dark brown ,get your toilet glazed brown,buy a stack of brown clothes and even buy a brown car!
See,no fucking problems,there's always a different way to skin a cat.
Marriage is the greatest fraud ever perpetrated on men.