Stain Removal, Bleach or Cal Hypo... how/what rate to add?
I'm in the first week of a 2 week iron stain removal routine (26K vynil liner IG). Per Ben's recommendations, I've brought the FC and PH down, got the stain off the the liner (used Pool Stain Treat - Oxalic Acid) and am now slowly bringing the PH up. I've been keeping the FC low, at 0~1.5PPM with tri-chlor tabs in the skimmer (pump/filter running 24x7) and have been adding polyquat regularly. The liner is clean and pool never looked so good!
In another day or two my PH will be up high enough so I can move onto the 2nd phase and start increasing the FC. I'll take the tri-chlor out of the skimmer and start to add bleach/Cal-Hypo.
My question is... I can't seem to find Cal-Hypo pucks anywhere around me. I can find the granules though... If I want to raise the FC slowly... how and at what rate should I be adding the Cal-Hypo granules through the skimmer? What if I use bleach? How do I slowly add bleach?
Additionally, why is it that Cal-Hypo or bleach is recommended for this process? My CYA is low (~25). Can't I just use Tri-Chlor tabs in the skimmer? Thanks!
Re: Stain Removal, Bleach or Cal Hypo... how/what rate to add?
You can keep a trichlor tab in the skimmer., but trichlor is acidic and if you want to bring up your ph it will be more difficult with it in. I never used oxallic acid, I've only used the ascorbic acid. The reason you would want to use bleach, is the ascorbic acid, and maybe also the oxallic acid eats up the chlorine very quickly. You would have to put a lot of pucks in the skimmer to get the chlorine up, and that isn't a good idea. You can just add the bleach about 1 gal at a time, take out the puck if you add bleach through the skimmer, or you can add bleach to the pool and leave the puck in. Trichlor will also bring your ph down, and it is hard to get your ph up sometimes after the stain treatment. You can also use the cal-hypo granules, but watch if you have high calcium. Just never mix different kinds of chlorine together - you can add them to the pool just not together, in the pool they are diluted. The reason you want to add the chlorine slowly is because if there isn't enough sequesterant in the water, the metal will fall out and stain again. Just keep adding the chlorine till you get the chlorine to 3ppms. since you have a cya of 25. Keep it on the low side for at least 2 weeks, and don't shock the pool for at least 2 weeks.
