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6 Month Ph Stabilization Product?


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Is there really a (new) product on the market that will keep the pH in the 7.4 to 7.6 range for about 6 months? Do the water experts and/or chemists in the group have any information? I searched the forum and could not find anything, but if it is there please point me in the right direction.

Yesterday I was in my local national retailer. In talking with the manager about my need to frequently lower the pH in my less than a year old plaster, 30,000-gallon pool with a salt/chlorine generator. He said that pools with salt/chlorine generators are always fighting high pH (I assume vs. those using acetic dichlor or trichlor products for sanitation). And, there is a new product they will likely start carrying early next spring that will maintain the pH in the optimal range for about six months. It is in testing now and showing good results. He expects the product to retail for about $60, which averages out to about $10 per month. If it really works, the new product cost would not be much of an increase for me and probably worth the extra money if it keeps the pH down. What’s the word?

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You mentioned in another pool forum that you wanted me to respond to this post, so I'm doing that here.

I am not aware of the product these guys seem to be talking about, but a new plaster/gunite pool will indeed show a strong tendency to increase pH, especially in the first year and especially in the first few months after installation. The reason is that the process of curing concrete absorbs water and produces Calcium Hydroxide which is strongly basic (alkaline). So you will find that both your Calcium Hardness and your pH both rise over time though the rise in CH is smaller than the increase in pH and the amount of acid you need to add.

There are other factors that cause the pH to rise in a pool, the most common being the outgassing of carbon dioxide which happens because pools are intentionally "over-carbonated" somewhat like a carbonated beverage (you do this by initially adding sodium bicarbonate to your pool). This is done to provide a carbonate buffer that reduces the amount of pH change caused by additions of acid or base to a pool and it is also done to provide carbonate ion so that when combined with calcium ion (which you add initially to a pool via calcium chloride) the pool is "saturated" with calcium carbonate (calcite). This is done to prevent corrosion of pool surfaces (and from grout in tile) while not being too much which would cause scale to form. This fine balance also coats some metal surfaces to inhibit corrosion though keeping the pH above 7.0 is generally a much more important factor for preventing the metal corrosion. However, this excess of carbonate in the pool means that it will outgas carbon dioxide to the air. When this happens, this is similar to adding base (alkaline) to your pool and the pH will rise (though unlike adding a base, the TA won't change). This process is accelerated at higher carbonate levels (usually higher TA), at lower pH and with increased aeration (e.g. waterfalls, spillovers, fountains). Using a pool cover, eliminating aeration features, keeping the pH at 7.5 or higher, and keeping the TA low (below 80, but don't go below 50), all help reduce the pH rise by reducing carbon dioxide outgassing.

A pool that uses a salt-water chlorine generator (SWG) also shows a strong tendency to increase in pH and I believe this is due to the increased aeration of the water caused by the hydrogen gas bubbles that are generated (if you don't see such bubbles during the day, try running your pump and SWG at night with the pool lights on). It is also possible for some excess chlorine gas to be generated and not get dissolved quickly enough, but I find that unlikely. Some people have found that lowering their TA reduces the rate of pH rise which might seem ironic since a lower TA means less pH buffering but the outgassing forces from higher TA are a little more important than the buffering loss at lower TA. Some people have added 50 ppm Borates (from Borax; technically the 50 ppm measures Boron) to their pool which has significantly lowered the pH rise as well as chlorine demand. This is probably because they run at lower TA due to the Borates doing some of the pH buffering and the Borates are an algicide that lowers chlorine demand letting one lower the SWG production and therefore less aeration due to fewer hydrogen bubbles.

So, back to your original question of this new "product". It could just be an additional buffer like the Borates. However, a pH buffer will reduce the amount of pH swing but it won't change the amount of acid you will still eventually need to add to restore pH. The buffer simply resists pH changes, but does so in both directions. So with a buffer, you may not need to add acid as frequently, but you will still need to add the same quantity of acid to get back to where you were. The exception to this is what I described above where the Borates have an additional benefit, especially for SWG pools, but that is not directly related to their buffering capability.

The other possibility for their "product" is simply something that automatically adds acid to your pool. Perhaps they have come up with another slow-dissolving solid acid that doesn't have CYA (and probably doesn't have chlorine either).

It is also possible that the "product" does something to isolate the hydrogen gas bubbles from the SWG generation so that they do not contact the pool water as much, but I doubt that this is what is done as it would be a one-time design change and not something you would have to buy every 6 months. It is also possible that the "product" is something that gets added to the water that is more easily reduced than water is to hydrogen gas (which is what the SWG does in addition to oxidizing chloride ion to chlorine gas) thereby generating less hydrogen gas so less aeration so less outgassing of carbon dioxide so less rise in pH. It would be tricky to find such a chemical since it can't be too easy to reduce or else the chlorine in the pool will oxidize it back to its original state, using up chlorine in the process (and it would have to somehow leave the pool or get converted into something else so that it doesn't get oxidized by the other plate in the cell).

See if you can find out more details about this "product".

[EDIT] P.S. I did a simple search on "pH stabilization pool" and found this link which refers to a SWG that also adds acid to maintain pH. However, what you described sounds more like a chemical addition than an automated pH detection and acid injection system. [END-EDIT]

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chem geek, thanks for the thoughtful reply.

I will check with the store manager after the first of the year but I may not be able to get any more information until after their March manager's meeting when he expected to get the okay to sell the "product" durning the 2007 swim season. However, being in Southern California where we do not close pools for the winter, I expect he will start selling the product as soon as it is in the store.

I will let you know when I get any more information.

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I do know that pH balancers have been available for spas for quite some time now and claim to keep the pH balanced for 3 months. Most of these products are either phosphate based buffer systems that can cause problems with calcium hardness in the water and, IMHO, should not be used or borate based buffer systems that are effective in keeping the pH in line for a longer period than without and also tend to reduce sanitizer demand because of their algaestatic action. The only way to automatically adjust pH with a SWG that I know of is by using a pH electrode and a peristaltic dosing pump to add acid to the pool such as is used in the Pool Pilot Total control system.

The pH of a pool is a dynamic beast that contains many variables. I seriously doubt that a product that will keep it in 'proper range' for 6 months is any more than just snake oil. Just my 2 cents! (and I would LOVE to be proven wrong on this one! It would make my pool much easier to maintain.)

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