super fine white/gray powder on sides and bottom of fiberglass pool

[Azger]

Pool- Fiber glass, 18000Gal, sand filter
FC-7
CC-0
CH - 275
PH-7.4
Alk-100

History - I posted before about discoloration (still have that issue) which we thought was metal build up in the water (still need to get that tested). We did do the ascorbic acid treatment that whitened the pool back up and it worked great but since then the darkening has returned. We are just going to let it get grungy until it gets to cold to swim and do another treatment.

However I noticed when ever I put in the pool robot or after swimming the pool would look a bit cloudy, doing nothing it always clears up on it's own and we have crystal clear water. Yesterday while swimming I noticed what looked like finger prints on the pool sides, basically in the discoloration so I rubbed with my hand and lot of this really fine, like super super fine dust, cloud poofed up and then dissipated into the water. I also noted that this "cleaned" the pool wall a little bit. Still discolored but lighter and the finger marks are gone. So my wife and I started doing it just with our hands all around the pool. I tried to capture some of the cloudy water in a cup but it looks crystal clear when I do. Of course after about 20 min the pool was super cloudy and we got out. This morning crystal clear again and I assume if I rub the sides it will poof up again.

I read on calcium scaling but nothing I read says it would be this super fine they always talk about scaling the pools surface is smooth to the touch and you can't notice a difference when the powder is there or after you rub a bit. Through out my testing our CH has always been 250-275 which is on the low side I was wondering if it was like that as the calcium was getting pulled out of the water and on my pool. Or could it be the fiberglass it's self? we had to refinished last year.

Stumped we are going to go to the pool store today to test metals just to finally put that to rest, the sequestrate we put in before should be pretty much done and gone. Any other Ideas?

We figure our sand filter isn't going to catch this stuff we were thinking of trying a clarifier, once in the pool jump in and start rubbing again make it super cloud and see if we can't get some of it removed. Not sure if this will be a wast of money though.

 

[Texas Splash]

There have been other members describing exactly what you are where it's not the chalkiness that is embedded and doesn't come off (unless sanded) but actually comes off as dust when wiping by hand. In some of those cases they increased the TA and/or CH which seemed to help, but we don't know why. By all accounts, your numbers look great. I doubt it has anything to do with metals. More than anything it's probably something about the gelcoat itself, either who it was made or applied. Your getcoat should not have any calcium product in it that requires an elevated CH level, but if you wish to increase the CH to about 300 as a test to see if helps that's always an option. Looks like you made a type with the pH right? Not 4.4, but maybe 7.4?

 

[Azger]

Yep

There have been other members describing exactly what you are where it's not the chalkiness that is embedded and doesn't come off (unless sanded) but actually comes off as dust when wiping by hand. In some of those cases they increased the TA and/or CH which seemed to help, but we don't know why. By all accounts, your numbers look great. I doubt it has anything to do with metals. More than anything it's probably something about the gelcoat itself, either who it was made or applied. Your getcoat should not have any calcium product in it that requires an elevated CH level, but if you wish to increase the CH to about 300 as a test to see if helps that's always an option. Looks like you made a type with the pH right? Not 4.4, but maybe 7.4?

7.4! fixed it in the main post. I will try to up the CH a bit and see if that helps at all.