Can ph minus be used for swg

[grottoguy]

The thread entitled "TFPC for beginners" (authored by JasonLion) states that Dry Acid should not be used for a SWG. I have a digital Autopilot and my PB uses PH Minus (which I think is dry acid) all the time. PH Minus contains sodium bisulfate, and my SWG does indicate the addition of sodium bisulfate is acceptable to lower PH.

Is there a reason that PH Minus should not be used with a SWG?

Thanks

 

[chem geek]

Some SWCG manufacturers say not to use dry acid but others do not. Presumably they are worried about calcium sulfate scaling, but it takes an awful lot of sulfate for that to occur. More generally, we recommend against continued use of dry acid in plaster pools because in this situation there is the known concern for higher sulfate levels attacking concrete/plaster as described in Sulfates - what's the problem? and Sulfates why so bad?.

 

[grottoguy]

Well that creates a dilemma as my PB gives me the PH Minus for free, but I have to pay for the Muriatic acid. Are the fumes from the acid harmful? Do others use Acid Magic (which eliminates most fumes)?

When you use the PH Minus, do you put it in the skimmer, or drop it near a return?

Thanks

 

[Patrick_B]

That's odd, because dry acid usually costs more when you figure the volumes needed. The fumes can easily be avoided if you get some during additions, and if you add acid as some do, there are virtually none. Some members simple hold the jug by the handle, rest about half the jug in the water, and slowly tilt it until acid starts coming out slowly. If you do that very slowly at a return in your pool, there wil hardly be any fumes at all, and splashing/spilling potential is virtually Zero.

 

[grottoguy]

Thanks Patrick. I'll try that. The reason I get the PH Minus for free is because my PB supplies chemicals and that is just what they use. If I were to use some PH Minus, how and where should I put in the pool?

I read some of the links posted above by Chem geek, but a lot of the embededed links are no longer valid. It seemed like PH Minus may cause problems for a plaster pool but the concentrations of Sulfates would have too be very high (and there wasnt much direct evidence on what such concentrations would need to be).

 

[Patrick_B]

I would not use it, but if I had too in a pinch, I would fill a five gallon bucket 1/2 full and add the acid to it and dissolve it. Pour that in very slowly in front a a return, and be very careful not to let it splash back on you or in your eyes. You could do the same thing I suggested with the jugs. Ask PB if they can get you MA at a discount. They should be able too for sure. I'd never use dry acid unless I was really in a bind to lower pH and had no other choice. I get four bottle cases at about 15.00+ tax from a pool builder supplier and he is still making money.

 

[DaninFLA]

MA is also pretty cheap and doesn't take that much in my experience. plus it doesn't leave anything in the water that cant be removed (sulfates). don't be scared of muriatic acid, it isn't that bad. just use common sense and just pour it right in the pool like liquid chlorine. no pouring into measuring cups, etc...just eyeball it based on % of the jug. eliminates the issues.

plus, I love having MA around the house. surprising how much you end up using the stuff when its on hand

 

[chem geek]

If you can find half-strength Muriatic Acid (15-16% Hydrochloric Acid) at roughly half-price, then that fumes a lot less than full-strength Muriatic Acid (31.45% Hydrochloric Acid).

I updated the links so the few that were broken should no longer be broken (see this post). As noted in this link, the Pool Water Treatment Advisory Group recommends keeping sulfates below 300 mg/L. Every pound of dry acid in 10,000 gallons increases sulfates by 9.6 ppm. So 300 ppm sulfate would be after 31 pounds per 10,000 gallons if there were no water dilution. There may also be some sulfates in the fill water, but usually that's fairly low.

 

[grottoguy]

Thanks. Appreciate it Chem geek