Yellow Staining, Acorbic Acid Works Well, BUT.....

[pilot-werx]

Hi All,

First post here and hoping Marie or anyone can help me out. After having black bark mulch blow into the pool on the few windy days we had, I began to notice the pool steps and liner begin to turn yellow. The pool is in-ground, 25000 gal, hayward sand filter, hayward super pump, raypak heater, inline chlorinator.

The people who put the pool in recommended sprinkling ascorbic acid over the steps and putting the rest (2lbs) in the skimmer. The staining went away within an hour. However, the moment I started to bring the chlorine up, the staining came back. Again, I did the ascorbic acid treatment and all was well until the I started adding chlorine back in...

I had emailed Alan at www.askalanaquestion.com and he said I should use ascorbic acid and follow that with Liquid Metal Out. Of course his website says nothing but good about the Liquid Metal Out, but has anyone here used it? If not, is there a Metal Out product that you have used? Since the local pool stores here carry nothing, can you point me in the direction of where I might be able to order?

Thank you for your help!

Regards,
Chris

[Watermom]

Hi, Chris and welcome to the forum! I'm going to alert Marie to take a look at this thread for you.

[mbar]

Hi Chris, welcome to the forum You always need to follow ascorbic acid treatment with a metal out (sequestering agent). Any good metal sequestering agent will do - good ones usually run about $20 a bottle. I have used Jack's Magic, Sequasol, Metal Magic, and a few others that all seem to work the same. I put the metal out in as soon as all the stain is lifted (about a half hour later). The reason you need a sequestering agent is because the ascorbic acid lifts the stain off the surface of the pool, putting the metals back into solution. The sequestering agent then holds the metals in solution keeping them from redepositing onto the surface of the pool. Try to keep your ph on the low side for a while. High chlorine along with high ph is what causes metal to fall out of solution. If the metals stains start to come back when raising the chlorine levels, take the ph back down to 7.2 , and add more sequestering agent - this will usually remove any light stains that are starting. Please give me a set of your pool chemistry numbers (ch, ph, alk, calcium, and cya). If you have any questions feel free to ask

[pilot-werx]

Thank you for the reply.

My numbers as of a few moments ago are:

chlorine : 0.5ppm
ph: 7.6
alkalinity: 90
calcium: 250
cya: 50

I am a little concerned with the chlorine that low as with the water heated to 82, it is only a matter of time before algae forms... However, right now the water is crystal crystal clear...

What are your thoughts on oxalic acid instead of ascorbic? The reason I ask is that oxalic is half the cost of ascorbic around here. I think there is a dealer close by that has Pro Teams Metal Magic. I will pick some up and try that.

How do my water balance numbers look?

Thank you for your help.

Chris

[chem geek]

People have used citric acid, which is also less expensive, and it seems to work but just takes somewhat longer. I know that oxalic acid is also a reducing agent so in theory it should work, but I don't know how well.

As for preventing algae, one usually adds PolyQuat 60 to the water when doing an ascorbic acid (or citric or oxalic acid) treatment in order to prevent algae from growing during the treatment.

[mbar]

I second what chemgeek said. I have used citric acid and it works well. You just have to use more of it. Here is a link to ascorbic that isn't too expensive:

http://www.msm-msm.com/store/agora.cgi


Here is one for citric acid:

http://www.chemistrystore.com/search...to+Search2.y=0

The rest of your numbers look good. I always use the polyquat 60 when doing the ascorbic acid - especially if the water is warm, you also want to keeep your ph levels at 7.0 to 7.4 while slowly raising the chlorine levels back up. Let us know how you do, and if you have any other questions

[waterbear]

People have used citric acid, which is also less expensive, and it seems to work but just takes somewhat longer. I know that oxalic acid is also a reducing agent so in theory it should work, but I don't know how well.

FWIW, oxalic acid is what is used in United Chemical's Pool Stain Treat and Pool Stain Treat spotting bags. I can't really tell a difference in how fast it works compared to Ascorbic acid but Citric does seem to be a bit slower. However oxalic acid is the most toxic of the three with ascorbic acid being the least toxic.