Question for the Chemistry Pros

[riverheightsnancy]

Out of curiousity I read the manual for my Taylor test kit yesterday because I never quite understood the Water Sat Index (Watergram) and really wanted to understand how to use it (if at all). Here are a few questions:

1) Is anyone using the CYA correction to TA table, why or why not?

2) If I want to increase my CH a bit (I have a concrete painted pool @ 170ppm) would Cal Hypo be acceptable in small doses now and then? I do add salt for water softeners into the pool. I am well below range as noted on this site. Does the salt make the water "softer" thereby affecting the CH? I am not seeing any nonbalance problems, just curious.

3) We have had massive amounts of rain in NJ this year. Can the water dropplets hitting the water cause a rise in PH similar to a jet or waterfall? I have had unusual PH/ALK readings this year. With the PH high and my ALK low. Just curious. I have not tested the rain water yet, but I may because of my suspicions about this problem this year.

4) Almost got pool stored yesterday, Went in for skimmer socks, a bottle of Jack's, and 1 replacement reagent for ALK. Upon check out they always ask how you are santizing your pool. With TFP in mind, I confidently say, "Liquid chlorine." (thinking to myself, Clorox honey). Well the guy tells me, I see you are getting some Jack's here, what kind of stain do you have? (He tried to convince me that my brown stains were copper, not). "You know how the chlorine is brownish, the iron is COMING from the chlorine because they use IRON to bind the chlorine." Now, I did not know what to say to that, as the bleach is brownish looking. I told him that when I use Trichlor (it's white), I get staining too. He said I needed to switch to something else to stop the staining. I stopped listening at that point because, I wanted to check with the pros here.

Thanks for the help.

 

[JasonLion]

1) We never use the CYA correction to TA here at TFP. The CYA correction to TA is only used with calculating LSI. That is all that it is, part of the LSI calculation. We normally use CSI, instead of LSI, which is calculated by my Pool Calculator. CSI uses the results directly from the test kit.

2) If you need to add CH anyway, and the amount of CH you need to add is relatively small, then using cal-hypo is very reasonable. Cal-hypo only adds CH slowly, so it isn't appropriate when you are in a hurry to raise CH significantly.

Salt doesn't soften the water at all, and has no effect on the CH level. However, the feeling of salt water on your skin is similar to the feeling of soft water.

3) Rain causes aeration, which can raise the PH, especially when TA is high. The rain water in the US is usually acidic, and ignoring aeration will lower the PH just slightly. There are a few areas when the rain water can be basic, and raise both PH and TA, but that is unusual. Normally the TA of rain water is very low, so aeration is by far the dominant effect.

4) As with many pool store explanations, there is a small grain of truth here, but the overall statement is misleading. Stains tend to get worse when the FC level is high and when the PH is high. Liquid chlorine/bleach raises the FC level and also temporarily raises the PH (the PH goes back down again as the chlorine gets used up).

For normal day to day use of bleach this isn't a big deal, the PH won't change very much. But if you are shocking the pool, bleach will raise FC and PH, while some other sources of chlorine will raise FC and lower PH. This isn't a big deal if you are using enough sequestrant, but can cause minor problems now and then.