Hi I have an inground vinyl pool- 28,000 gallons and recently have had issues with brown looking stains in the pool. We had our 5 year old heater replaced this year because the heat exchanger corroded. I am assuming because of metals in the water.

This year when we opened the pool everything looked OK but within days we saw what looked like dirt on the sides of the pool-thought it was sand because we had the sand in our filter changed-pool guy said it was dirt-we vacummed it, set the fileter to waste and all was good except that brown spots starting showing up along the sides not too many but seems like it getting worse.
Husband went to pool store and they said it was iron.
I'm just a bit confused, are iron and copper stains the same. I read about using vitamin c to detect iron will this also detect copper.

Thanks,
Daisy