Alternative to ascorbic acid to remove stains

[illinipdx]

it is a vinyl liner pool

When you say drain and refill, how far? We can't drain too far, can we?

[waterbear]

without a vacumn behind the liner you will have to drain to just a bit below the skimmer and refill repeatedly to dilute the CYA

[DavidD]

illinipdx,
I have used Stain Free several times and it works great. Evan is correct that you can get the same thing for $8.50 per lb if you order the 9lb pail through the chemistry store http://www.chemistrystore.com/Ascorbic_Acid.htm. I ordered the 2llb pail last time thanks to Marie (mbar) and it worked great. I'll never buy the Stain Free again unless I'm in a real bind due to its high price.
Now, since you have started the this thread, I have another question that fits within the topic so I'm going to piggy back your thread. Maybe Evan or Richard can help.
How about Oxalic acid? Is it any more dangerous than ascorbic? Does it work for stain removal? Here is the info: http://www.hydropool.com/cgi-bin/hyd...d_chem/pst.htm I recently picked up a 2 lb jar for $15 and thought I might give it a try but I guess I'm a little partial to the ascorbic since I know "it's just vitam C."

Dave

[waterbear]

From what I know oxalic acid is more toxic than ascorbic acid (if you read the caution statements on the bottle of oxalic acid product that are absent from the ascorbic acid product you will see what I mean) but works in much the same way. It is extremely effective on iron and to the best of my knowledge is the only thing that really works on cobalt staining in fiberglass pools. (Someone please correct me if I am wrong on that!)

[DavidD]

From what I know oxalic acid is more toxic than ascorbic acid (if you read the caution statements on the bottle of oxalic acid product that are absent from the ascorbic acid product you will see what I mean)

Yeah, I noticed that. It did say it was still safe to swim but it definately seems more toxic.

but works in much the same way. It is extremely effective on iron and to the best of my knowledge is the only thing that really works on cobalt staining in fiberglass pools. (Someone please correct me if I am wrong on that!)

Do you have any idea what color cobalt stains would be and what would cause them?

Dave

[waterbear]

cobalt staining looks like greyish or black spots on the fiberglass. Not sure of the cause but some things I have read seem to point to low calcium levels in the water.