Lower TA or Borates

[fanis.merk]

Hello,

My fill water has 7.4 pH, 300 TA and 650 CH. It is an overflow pool with a lot of aeration and SWG. pH creeps higher quite fast. Everytime I open the pool I smack the TA down with Muriatic Acid to lower the acid demand and maintenance rest of the season. However going from 300 to 50 is not an easy process as the pH goes down as well. You need to do it step by step, i.e. smack and aerate, and loop. It takes a long time. I have no experience with Borates. In my scenario is adding Borates a better option? It seems Borates are a more optional chemical. I would like to understand why (why we take the TA lowering approach first).

 

[mgtfp]

With this fill water you want to reduce TA not just to make pH rise more manageable, but also to get CSI into a manageable range to limit calcium scaling to a bearable level.

Borates will certainly help, especially with scaling within the SWG cell, but I don't think you can just ignore TA.

Borates help to reduce the rate of pH rising, but they don't remove the cause of the pH-rise, only reducing TA will do that. With Borates you reduce the frequency of having to add acid, but then you'll have to add more acid to achieve the same drop in pH, so in total you don't really change the amount of acid needed, you just don't have to add it as often, but each addition will be larger.

When adding acid manually, it is a great benefit not having to add acid as often, but with an automated dosing system, I don't really see much benefit by Borates from an acid adding frequency point of view.

To reduce scaling of the SWG cell, Borates could actually make sense in your case, but I don't think this will make reducing TA unnecessary.

 

[fanis.merk]

With this fill water you want to reduce TA not just to make pH rise more manageable, but also to get CSI into a manageable range to limit calcium scaling to a bearable level.

Borates will certainly help, especially with scaling within the SWG cell, but I don't think you can just ignore TA.

Borates help to reduce the rate of pH rising, but they don't remove the cause of the pH-rise, only reducing TA will do that. With Borates you reduce the frequency of having to add acid, but then you'll have to add more acid to achieve the same drop in pH, so in total you don't really change the amount of acid needed, you just don't have to add it as often, but each addition will be larger.

When adding acid manually, it is a great benefit not having to add acid as often, but with an automated dosing system, I don't really see much benefit by Borates from an acid adding frequency point of view.

To reduce scaling of the SWG cell, Borates could actually make sense in your case, but I don't think this will make reducing TA unnecessary.

Great answer. I actually have automated acid dosing. If I don’t initially reduce the TA it is actually disabling itself once it realizes it is feeding too much acid and showing TA error on the screen. So I always start the season by manually reducing the TA first, but it is a cumbersome process. After that it is smooth sailing other than the fact that I consume substantial amount of acid. I was hoping borates would help, but according to what you said it is actually kind of useless from that perspective.

 

[mgtfp]

How are you keeping your SWG plates clear from scaling? With your fill water CH and TA that must be a challenge.

Keep in mind that by following the manufacturer's advice of using diluted HCl (or another strong acid) to clean the cell shortens the life of the cell significantly. Each time you use a strong acid to remove scale, you also remove some of the Ruthenium oxide coating.

Best to avoid scaling in the first place. That's where Borates could make sense for you. Even though they will not really reduce them total amount of acid to be added to keep pH rise in check and control TA, they are a very effective buffer around pH 9, and limit the localised pH rise around the SWG cathode a lot.