purple residue

[allinpoolcare]

I service many pools and am baffled by this one. One account has a purplish powery residue all over the walls and floor, and is now leaving stains on tile and grout. cya is 150 plus, ta is 120 ph is 7.2 calcium is about 500ppm, water just wont hold a chlorine residual. I know that there is chlorine in the water, due to the fact that I get no algae nor had I had a problem with it over the summer. Just can't get a chlorine reading, with strips or with a taylor titration kit. Now I have the purple. Customer wont drain or partially drain pool for me says he cant afford it. Question is, is there any way to reduce or elimate the cya level without a drain and is there any way to treat the purple staining

[mr_clean]

it's way to high of CYA which will start producing purple residue.
when CYA get 100 or above chlorine gets less effective & sense it's getting colder out, is probably why algae is not growing yet.

stop using tabs & go with liquide chlorine for now. Also if you can backwash filter do it everytime you show up & do it longer than normal so you can lower CYA dispite customer.
Also let customer know staining problems will be do to him not allowing you to drain some water.

[Dax67]

I had a purple ring develop around the perimeter of my pool last year. It seemed that the copper content of my pool was very high. I also had never completely drained my pool since it was built (5 years) -- something I was told should be done every few years or so to flush mineral/chemical buildups.

My solution, I completely drained the pool and sprayed muriatic acid on the purple stains. The stains dissolved instantly and I haven't had a problem since.

Also, what was so perplexing about the stains, was that my water sample indicated that all was correct since they don't normally check for copper.