OFFICIAL water chemistry guidelines-what are they?

[Vinny]

Since I don't have a problem with TA and PH as they rise and fall together I can't comment on what you've said. Your method does work for me and as I said I "know" my alkalinity is in line with my PH based on my water testing and watching the TA and PH rise and fall, when I add baking soda I see my PH rise if this the result of out gasing as you suggest - great; I know that adding baking soda will make my TA rise.

The ONLY problems that I have with your method and this might come from my ignorance is that your method doesn't necessarily work for everybody. I've seen posts where people have high TA and low PH - if they drop the TA by using acid then PH will drop as well. And my pool water has been at 95º, a high TA but the PH stayed the same.

I stopped posting/viewing poolsolutions a few years ago. I do pop in from time to time but a lot of what is being said now on other websites came from that website. Maybe the info out of it has evolved through the years and I remained stagnant in my knowledge, chemgeek wasn't around that website when I was active there. I don't doubt what you say but it doesn't seem to jive with what used to be said on the poolsolutions website or what professionals say. Maybe spa water is different than pool water and it does seem to act differently at times for me.

I guess it might be time for more internet water chemistry classes!

[Nitro]

The ONLY problems that I have with your method and this might come from my ignorance is that your method doesn't necessarily work for everybody. I've seen posts where people have high TA and low PH - if they drop the TA by using acid then PH will drop as well. And my pool water has been at 95º, a high TA but the PH stayed the same.

The only reason why pH would remain low (<7.4) despite TA being high (>100), is if there is little aeration. ie. in a pool, or hot tub with few air/jets. However, anyone with many jets/air in their hot tub will experience pH rise, if TA is high.

I stopped posting/viewing poolsolutions a few years ago. I do pop in from time to time but a lot of what is being said now on other websites came from that website. Maybe the info out of it has evolved through the years and I remained stagnant in my knowledge, chemgeek wasn't around that website when I was active there. I don't doubt what you say but it doesn't seem to jive with what used to be said on the poolsolutions website or what professionals say. Maybe spa water is different than pool water and it does seem to act differently at times for me.

I'm not sure which site was around first, but I learned most of this stuff from PoolAndSpaForum and TroubleFreePool. Chem Geek (the expert) posts on these forums regularly, and has taught me a lot. Waterbear is another expert who I learned a lot from.

I guess it might be time for more internet water chemistry classes!

Check out this post where I documented the latest knowledge in Water Balance and Sanitation using the Dichlor/Bleach method. I just compiled this info from other sources and posted it in one place.

[Chad]

Alright. I'm fairly certain I understand, to some degree atleast, everything being discussed in this thread. The whole aeration thing is a bit new but I think I get the jist of it. The only thing is that my water apparently doesn't follow some of the characteristics of a hot tub being exposed to a high amount of aeration as some are stating...maybe I just overlooked something. Anyways, here's a little info on my water-

* all tests are done with the Taylor k-2005.

-out the tap  pH 8.0, Alk 100-110, CH 150-180. No signifacnt change once my spa is filled and heated with the source water.

-Through the past two years I've learned not to adjust anything, as the alk and pH ALWAYS fall together. I seriously only add dichlor for atleast a month after a refill. I test my pH every week. When she finally drops below 7.2, I test Alk as well(it's typically < 80 by then) and adjust them accordingly with Sodium BiCarbonate. I do this maybe 2-3 times a fill(typically 4 months) and that's it.

-I soak almost everyday and I ALWAYS have the air injectors on when I do. What's got me confused is that according to the 'aeration effect' and my intial readings out the tap, my pH and Alk should be climbing not falling, right??

[chem geek]

I seriously only add dichlor for atleast a month after a refill.

The consumption of chlorine is acidic so even though Dichlor is initially nearly pH neutral upon addition, when the chlorine gets used up this is the same as if you added acid to the water.  In 350 gallons, the addition AND subsequent consumption of 4 ppm FC from Dichlor is identical to 1.2 teaspoons of dry acid in terms of the effect on pH if there were no outgassing.

If you wanted your pH to be more stable in your situation using Dichlor, you could have the TA be even higher.  The pH rise from outgassing would then balance the pH drop from the Dichlor addition and consumption.  Over time, the TA would drop and you'd need to add more, but by then some of the TA measurement will be CYA (about 1/3rd, at pH 7.5) built up from the Dichlor and the CYA does not outgas.  However, you already have fairly high CH so you wouldn't want the TA to get much above 110 ppm anyway in order to prevent scaling.

Richard

[Nitro]

Chad,

As Chem Geek mentioned, adding Dichlor is the same as adding acid. This will lower your TA and pH over time, therefore counteracting pH rise due to aeration.

Vinny (I assume from a prior post) and I switch to bleach after a week or so of using Dichlor. Bleach has a relatively netural effect on TA/pH, so pH rise from aeration is more apparent. If you only use Dichlor, you can try raising your TA higher, which will prolong your pH from dropping.

[Chad]

The consumption of chlorine is acidic so even though Dichlor is initially nearly pH neutral upon addition, when the chlorine gets used up this is the same as if you added acid to the water. [glow] In 350 gallons, the addition AND subsequent consumption of 4 ppm FC from Dichlor is identical to 1.2 teaspoons of dry acid in terms of the effect on pH if there were no outgassing.[/glow]

If you wanted your pH to be more stable in your situation using Dichlor, you could have the TA be even higher.  The pH rise from outgassing would then balance the pH drop from the Dichlor addition and consumption.  Over time, the TA would drop and you'd need to add more, but by then some of the TA measurement will be CYA (about 1/3rd, at pH 7.5) built up from the Dichlor and the CYA does not outgas.  However, you already have fairly high CH so you wouldn't want the TA to get much above 110 ppm anyway in order to prevent scaling.

Richard

Thanks Richard. I especially apreciate the highlighted statement...very useful information!

[chem geek]

Probably even better is to say that [glow]the addition and consumption of 2 teaspoons of Dichlor is identical to 1.2 teaspoons of dry acid in terms of the effect on pH if there were no outgassing[/glow].

The above statement is independent of spa volume.  I should note that "outgassing" refers not only to carbon dioxide outgassing that raises the pH when there is higher TA, lower pH and/or more aeration, but also refers to chlorine outgassing.  The latter doesn't happen very much.  You can partly see this from typical FC usage when there is no spa use (some chlorine use also comes from a slow oxidation of CYA by chlorine).  Any chlorine that outgasses and doesn't get consumed in the water will not be acidic so the net result would be more of a pH rise (or less of a pH drop).