Whole Pool Stain, Rough Plaster at Season Open

[waterbear]

I am curious what your calcium was when you closed the pool. It almost sounds like scale deposits to me.
Edit: we tend to forget that calcium is also a metal.

[squirrel49]

Thanks for the replies so far.

A little more info.

1. I didn't measure CYA because I was out of the regents I need. I'll try to get a measurement tonight.
2. I don't remember if I closed with a high chlorine level. I did use chlorine-free shock when I closed.
3. I shocked with chlorine (bleach) when I opened.
4. I also tried crushed up vitamin C in a sock-- didn't seem to make a difference.
5. Checked my log... Calcium was at 350 when I closed.

Pat.

[mbar]

The reason I asked about the cya, is that mine usually is gone when I open my pool in the spring. If the cya is low, then the chlorine is much more potent. Your calcium last year was fine. One of the reasons I suggested the ascorbic acid treatment is that you said you used a solution of muriatic acid on your spa to get rid of the stains. I think the ascorbic acid would work. I know that on my fiberglass pool some of the stains felt rough to the touch, I don't know if it is a little scaling with the stains, but the ascorbic acid removed it. I have also used a light sandpaper to remove some stains that were very localized. You may be able to use a pumice stone. It is worth a try if the stains aren't too large. Just rub gently, because you don't want to take much of the surface off - just the stains. Hope thsese ideas work. Let us know how you do.

[waterbear]

Thanks for the replies so far.

A little more info.


5. Checked my log... Calcium was at 350 when I closed.

Pat.

Your calcium dropped 130 ppm while the pool was closed. I suspect it has deposited as scale, which is often seen as a rough white or tan deposit! Acid and/or abrasive scrubbing will remove it. You said your pH was over 8.0 when you opened. High pH is one of the factors that will cause scaling. You might try dropping your pH to 7.0 for a while to see if it helps redissolve any of it but the only solution might be an acid wash if it is really bad. Anyone else have any ideas on this?

[mbar]

I read somewhere that the scale that is brown is scale that formed over some dirt. This may have happened over the winter since there was such a calcium drop with high ph. I would do as Waterbear suggested. Take the ph down to 6.8 to 7.0, then brush the surface of the stain - even using a pumice stone. If the area of the stain isn't too big, this should do it, otherwise you will probably have to have the pool acid washed. Let us know how you do

[squirrel49]

Thanks for the replies.

I'm pretty sure you're all right on the mark. I think it is calcium scale. I went swimming tonight with a snorkel mask and inspected most of the pool. The surface is extremely rough (feels crystaline). It covers the entire pool, other than the foot or so that was not under water over the winter (that part is smooth). On the bottom, and all steps, it is tan, and on the walls and vertical surfaces it is white or colorless. I have a Merlin mesh safety cover that lets in fine silt over the winter so I think what I have been calling stain is actually dirt-covered calcium scale. This did not happen in prior years, but I don't remember opening at such a high ph level before.

I am willing to do whatever it takes to get rid of it. I would like to try every alternative other than draining the pool. The pool is appox 28K gallons and costs ~ $900 in fill water to fill it. I'm sick to my stomach because our pool plaster has always been baby smooth and now it feels like volcanic lava.

I will first try dropping the PH to ~ 7.0 and do a lot of brushing. So far brushing doesn't seem to do too much. I only have a nylon brush, should I buy an aluminum one? Is there anything else I should be doing? I don't know that a pumice stone is an option. The scale seems to be on every square inch of the pool.

Btw, my cya level is ~50.

Thanks,

Pat.

[Lenny]

Have you had any luck, Pat? I have the same problem, although maybe not as bad as you. Tan stains and roughness. I have a mesh cover too.

This is my second opening. The first closing was right after completion of the build, so I think my plaster has still been curing and causing my PH to get high very fast after closing. Both years my PH was sky high upon opening and my hardness and alk were both low.

Tomorrow I'll try dropping the PH and giving it a good brushing.

[squirrel49]

No luck yet. Consensus seems to be that I will have to drain and light acid wash or sand/buff to remove the roughness. I am trying anything I can to avoid that. The pool is relatively new (2 1/2 years).

We have dropped the PH and we brush twice a day now and my wife optimistically thinks is is getting slightly better --- I don't really see any difference yet.

This is my second opening as well, both with a mesh cover. One difference is that the first year I had not yet started the salt system on my pool, so it was closed and opened as a fresh water pool. Opened fine, plaster as smooth as ever. I brought the Salt system on-line last year, so this was the first year it was closed/opened with salt water. Could this be a contributor? Are you running a SWG?