A question about using Sodium Carbonate and Disodium Metasilicate and effects on pH

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T

three4rd

0
Jul 20, 2014
206
Berks County, PA
Hi,

I recently started adding Aqua Finesse Pool Care tablets to my pool since they are supposed to help with eliminating biofilms, slime, water mold, etc. A concern I have is that both of the ingredients, sodium carbonate and disodium metasilicate, are basic and so will increase the pH. This is a bit frustrating since I am already adding lots of acid to lower pH as a result of recently having had the pool replastered. My plasterer thought that the pH would settle down after the first season but yet here I am 2 years later seemingly battling pH increase more than ever, even though other readings are pretty decent (TA=110, CH=220). So it seems that the tablets are essentially adding pH increaser, while I'm adding pH decreaser!

What I am wondering is: will the tablets increase the pH to a certain point until they dissolve (in the skimmer) and then nothing beyond that point until they are added again the following week? Or will these two ingredients result in a constant increase? This scenario sort of feels like 2 guys in a canoe who are both paddling in different directions and not really getting anywhere!

Will the pH start to settle down during this season? I don't understand why the plaster - which is well cured by now - would continue to cause higher pH levels. I'm actually more concerned about that than countering the effects of the Aqua Finesse.

Any explanation very welcomed!! Thanks!
 
If you maintain proper chlorine levels (depending on your CYA), then there is no concern about biofilms, slime, water mold, etc.

We also do not really recommend putting tablets in skimmers.

Looking at the MSDS of those tablets ... I am not sure what the point of them is. They are:
25-50% sodium carbonate (soda ash, raising the pH and the TA a little)
20-25% sodium silicate (no idea what that is for)
10-20% sulfuric acid, aluminum potassium salt, dodecahydrate (lower pH and add sulphates?)

Seems like a product looking for a problem to solve.
 
Jason,

The OP neglected to mention that they operate a Baqua pool. So chlorine is not an option.

Three4rd,

Your rising pH is likely due to your high TA. I would recommend you lower it to 80ppm and see what that does for your pH stability. However, the chemicals you are using are going to be a constant source of pH rise and TA rise so this is going to be an ongoing battle.

As we talked about at the end of last season, you are on the losing end of the Baquacil battle. Your pool is just going to get progressively harder and more expensive to manage. This may be the season where you need to decide to dump the Baquacil and switch to chlorine.

Good luck,
Matt
 
Jason...LOL...no problem! I should have mentioned that this whole thing is associated with trying to forge on with baquacil. I appreciate your input!!

Matt....thanks as well. Yeah...you pretty well nailed it. With all due respect, I'm not convinced of being on the "losing end" of the baqua battle quite yet. Not just yet....IF these tablets do not do what they are supposed to do in the way of keeping the biofilms, slime, etc. in check, then I think that the chlorine conversion is forced upon me. Contrary to the extreme affection for using chlorine around TFP, I really don't want it, don't like it, but may have to go back to it. I have many bad memories of using that stuff. I have no problem with baquacil with the exception of recurring pink slime. I know the chemicals are more expensive, but I'm truly not concerned about that.

Anyway...how do I lower the TA without also lowering the pH? I think aeration is one of the ways this is accomplished, but I don't have any such devices in the pool that would accomplish that. Acid would also be used to lower TA, right? Which would involve a subsequent reduction in pH....
 
I understand your bad memories of chlorine but I can say this - everyday dozens of pool owners come to TFP with horrible pool water management experiences which are mostly predicated on the really bad advice received from pool stores and so-called "experts". Then they try our methods of pool management and can't believe how much easier and cheaper it is. Someday we'll convince you, were patient....

As for your immediate question - you use acid (preferably muriatic acid) to lower your pH (and TA) to 7.0-7.2 range and then you aerate your water to raise the pH back up to 7.6 (TA is not raised by aeration). Each cycle of acid/aeration lowers your TA a little at a time. Unfortunately for you, you are using pool products that will raise TA, so that's working against you.
 
JoyfulNoise said:
I understand your bad memories of chlorine but I can say this - everyday dozens of pool owners come to TFP with horrible pool water management experiences which are mostly predicated on the really bad advice received from pool stores and so-called "experts". Then they try our methods of pool management and can't believe how much easier and cheaper it is. Someday we'll convince you, were patient....

As for your immediate question - you use acid (preferably muriatic acid) to lower your pH (and TA) to 7.0-7.2 range and then you aerate your water to raise the pH back up to 7.6 (TA is not raised by aeration). Each cycle of acid/aeration lowers your TA a little at a time. Unfortunately for you, you are using pool products that will raise TA, so that's working against you.
Click to expand...

Actually I don't use muriatic...I use granular BioGuard Lo n Slo. You guys might convince me...that's true...but I have a really hard time thinking about actually dumping bleach into the pool! I was at a hotel one time when I saw the owner come out and do that and was quite horrified really. Also, I have no means of aerating the pool. My return lines don't have any sort of threading at the end to be able to hook up some device that would accomplish the aeration.

Again, thanks so much. I'll just forge on here and see how things go.
 
Well, I hate to say this but you really need to reboot your thinking here. I'm not trying to sound snarky or rude but your opinions about what chlorine is and what is does are just not grounded in science. Yes, chlorine can do bad things and when used improperly you get horrifyingly bad results. But anything used improperly can be both dangerous and damaging. When used properly, chlorine is one of the most safe and effective disinfectants mankind has at its disposal. The advent of chlorine sanitation at the turn of the last century has saved far more lives than it has injured. I'd be far more concerned with all the unhealthy junk and chemicals used in a Baquacil pool than a chlorine pool any day. But, to each his own.

And, if you value your new plaster, you'll stop using the Lo 'n Slo. It's sodium bisulfate dry acid and you are building up sulfates in your water. Not only does calcium sulfate form and scale out onto plaster surfaces but sulfate buildup in your water is damaging to plaster. Sulfates can be absorbed into the plaster surface and cause the formation of sulfate salts in the plaster matrix which create high crystallization pressure and weak bonds which ultimately results in plaster cracks. See this page -

Sulfate attack in concrete
 
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