I used the test kit ($10) and ID'd the stain as calcium scaling. Then used 64 oz (2 bottles - $25 ea) of the magenta stuff and about 23 lbs ($35 / 5#) of the calcium scaling and copper stain remover. After a week I added 12 more onces of The Magenta stuff and will contunue to add a maintenance amonut for a few weeks. They have a written process in PDF form that is easy to follow. I can send it to anyone that is interested. It is not cheap, but was fairly successful.