Dry acid is sodium bisulfate. After dissociation of the acid salt, it leaves behind the sulfate ion. Sulfates can damage concrete & plaster as well as degrade the coatings on SWG plates. At high enough concentrations, sulfates can react with calcium to form spindly, needle-like crystals of calcium sulfate (gypsum). Sulfates can only be removed by draining water. While its use in vinyl pools is typically not as problematic as in plaster pools, scaling of gypsum crystals can increase the risk of liner puncture.So do sulfates cause any issues on vinyl pools? It seems like it's all about issues with grout in the threads I've found. The dry acid isn't THAT expensive, so I'd prefer to stay with it if I can.
Be careful with a mask -- there was one person here who put on a full respirator, and ended up with an eye injury that required time and ophthalmologist care to heal; clearly exposed to a lot more fumes than they otherwise would have tolerated.. Honestly I think it's better to not use a mask and to back away as soon as you smell any fumes. I do wear goggles to protect against splashes (but not gloves, because my understanding is that getting it on your skin isn't a major issue if you rinse it off ASAP)I use Dry Acid, despite the recommendations against with my SWG because I used MA once and was overwhelmed with fumes. I live in a very windy area of the country, the air is seldom still, and the wind only stays in one direction if there is a storm. Otherwise it changes direction every couple of seconds. Trying to get downwind of the stuff was almost impossible. My SWG is on it's 9th season with no issues.
That being said, I use acid seldom, maybe once or twice a year. But I have a problem with pH drifting low, not high, I believe because my fill well water is <7. If I had to use it as often as others do, I might get a mask and deal with the MA.
I may be overly paranoid, but I get nervous when I hear people say this, maybe because I'm picturing someone dragging a huge pail of sloshing water+MA (diluted but still very acidic) across the pool deck; seems to invite a lot of changes to spill on clothes, the deck, etc. To me, getting into a stable position at the edge of the pool, opening the MA jug, and pouring it from an inch above the water seems much safer. In the pool, you can put the jug itself partly in the water so the spout is very close to the surface, which you can't really do when pouring into a narrow bucket. I got that technique from people here, after initially doing the pour-into-a-measuring-cup thing until I saw one night by flashlight just how much fume came from doing that.+1 to safety glasses for working with muriatic acid, and +1 to muriatic acid for the pool.
Getting comfortable with MA by using the weaker percentage for a while is a good idea.
My better half gets a half full pail of pool water first, then adds the acid into that water. This kills the fumes right away. Water from the garden tap would be fine as well. Then she takes the pail to the pool for pouring it in.