Nature 2, Chlorine And Mps

[chem geek]

The product with a pH of 8 probably had some acid in it, though I don't know how they keep them from reacting as you normally never want to mix acid with hypochlorite sources of chlorine in concentrated form (it produces chlorine gas).

Anyway, the higher pH of the hypochlorite sources of chlorine does initially raise the pH of the pool, but the chlorine, which is hypochlorous acid, breaks down from sunlight producing oxygen gas and hydrochloric acid or it oxidizes ammonia (and urea) producing nitrogen gas and hydrochloric acid. So the consumption of chlorine is acidic and exactly counteracts the initial rise in pH so hypochlorite sources of chlorine are actually pH neutral (except for some "extra lye" in some bleaches, mostly off-brand Ultra, and in chlorinating liquid, but this is still relatively low).

When accounting for the consumption of chlorine, Dichlor is actually acidic, not pH neutral. You don't see this in a spa due to the high aeration and outgassing of carbon dioxide which would raise the pH, but in a pool you see it -- there was a user (I think on this forum) who used Dichlor for shocking and found the pH drop quite a bit after the chlorine levels dropped back down and the above explanation was why.

Richard

[waterpen]

When accounting for the consumption of chlorine, Dichlor is actually acidic, not pH neutral. You don't see this in a spa due to the high aeration and outgassing of carbon dioxide which would raise the pH, but in a pool you see it -- there was a user (I think on this forum) who used Dichlor for shocking and found the pH drop quite a bit after the chlorine levels dropped back down and the above explanation was why.

Richard

OK. So I think I get it. The Dichlor has a neutral ph but as the FC is used up, it actully becaomes acidic. However, this is more or less offset by the CO2 produced from aeration, likely resulting in a neutral ph.

However, the Lithium probably starts off with a higher ph (say around 10) and, as with any other hypochlorite source, the ph drops as the FC is used up. The CO2 produced from aeration raises ph, so the net effect may be a somewhat a basic or alkaline ph with the use of lithium.

Thanks

[chem geek]

You got it. The main point, though, is that there's nothing different about lithium hypochlorite and sodium hypochlorite (bleach or chlorinating liquid) in your last example -- even Cal-Hypo is similar. All of these hypochlorite sources of chlorine are, when accounting for chlorine usage, close to pH neutral so if your TA is high and you've got aeration then your pH will rise. Of course, understanding this means you can lower your TA and minimize your aeration (or use a pool cover) to stabilize the pH.

The chemistry behind this is here and a discussion about this where I am apparently still unable to properly articulate it is in this thread. We also had heated discussions about this on this forum as well and I pissed off TinyBubbles so much that he left this forum to go elsewhere (I still feel really bad about that). I did learn, however, that the aeration in the spa is hugely significant and that an ozonator contributes to that greatly so that from a practical point of view using hypochlorite sources of chlorine in a spa doesn't work for most people unless they are willing to add acid almost every time they add chlorine. Not only does carbon dioxide outgas, but I suspect hypochorous acid as well (especially if you can smell the chlorine). The exceptions where using hypochlorite in spa works are those with minimal aeration jets and no ozonator and where the TA is kept lower -- even so, most still experience a pH rise but it's manageable without daily maintenance for pH.

So while using hypochlorite sources of chlorine for pools is quite reasonable, it is something only for more advanced users and specific situations in a spa (and would be done with initial Dichlor usage for a week to build up a CYA level and then switching to bleach, preferably Clorox Regular since that seems to have the lowest amount of "extra lye").

Richard

[waterpen]

You got it. The main point, though, is that there's nothing different about lithium hypochlorite and sodium hypochlorite (bleach or chlorinating liquid) in your last example -- even Cal-Hypo is similar. All of these hypochlorite sources of chlorine are, when accounting for chlorine usage, close to pH neutral so if your TA is high and you've got aeration then your pH will rise. Of course, understanding this means you can lower your TA and minimize your aeration (or use a pool cover) to stabilize the pH.

The chemistry behind this is here and a discussion about this where I am apparently still unable to properly articulate it is in this thread. .....The exceptions where using hypochlorite in spa works are those with minimal aeration jets and no ozonator and where the TA is kept lower -- even so, most still experience a pH rise but it's manageable without daily maintenance for pH.

Richard

Wow everything you wanted to know about water chemistry but were afaid to ask!

You mentioned that using an ozonator also adds to the ph rise. What about the use of an UV sanitzer? Note that is is NOT the old type of UV based ozonator system. It is a new product from Beachcomber (I think it's actually made by Delta).

Thanks for the load of information. It'll take me a while to digest it all.

[chem geek]

It's the aeration of the water by having the ozonator inject air bubbles that causes carbon dioxide to outgas and have the pH rise. Pools and spas are intentionally over-carbonated to provide a pH buffer, but ironically the outgassing of carbon dioxide causes the pH to rise. So having a high TA which is supposed to stabilize pH can actually CAUSE it to rise.

As for a UV system, it depends on how it works. If it is only shining UV through a tube, then that should be no problem as no air is getting injected so no additional aeration.

Of course, aeration jets are the most powerful form of aeration though you usually do not run them very long. So being able to turn those jets off except for the one you are using would also be helpful in keeping the pH rise to a minimum.