Wow. Okay, so turn on water feature and just keep adding the muriatic in 15-30 min increments til we get it down. 👌 Got it. Thanks.
Just to clarify...
You're adding muriatic acid every half hour with the pump running to bring your pH
down. Every time you bring down your pH, your TA will come down some, too. You can actively pursue lowering your TA, which will help with the constantly rising pH, but you might not need to. Your new finish is drinking acid, which needs to be replenished, and this might be all you need to do to stabilize your TA at the same time.
When I first took over my pool, I was obsessed with lowering my TA. I built in-pool sprinklers for that purpose, and ran my pump all the time to aerate the water. And it was working, but it was a lot of hassle. Marty kept telling me "leave it alone, and it'll come down on its own" but I was determined. So I battled TA for a while, and it was coming down, but then it got old, dealing with the sprinklers, so I finally gave up and left it alone, and it ended up coming down and stabilizing all by itself, just as Marty said it would.
So it's up to you, and it wouldn't hurt to post your fill water TA, so we can see what you have. But I have high TA in my fill water, and my regular acid additions control both my pH and TA just fine, no special attention needed for the TA.
Regarding your concern about the constant pH battle... Your pH test is reading 8.0, so you plug that into Pool Math and then add the recommended amount. Only to later see that your pH is still 8.0. Sound familiar? This is probably what's going on: your kit only reads to 8.0, but your pH is likely somewhat higher. Maybe 8.2, or 8.4, who knows. But you plug in 8.0 and you dose accordingly, and your pH does come down when you do. But only from 8.4 to 8.2! Or 8.6 to 8.0. Whatever. You can't tell. But each time you test, you get 8.0, regardless if you actually lowered it some, because you're never getting below 8.0, to a level you can actually read from your test!
So what you need to do is what PoolGate is suggesting. You keep dosing acid until you get into the 7s. Then, and only then, do you actually know what the pH is.
So, you test, you get 8.0 and dose accordingly, say down to 7.6. Then you test again in 30 minutes (pump running) and see what you get. If you get 8.0 again, then you dose again, down to 7.6. You keep repeating that until you actually get 7.6. Then ideally you figure out how many times a week you need to dose with acid to maintain your pH in the 7s. If you test the next day, and it's above 8 again, then even once a day might not be enough. Try to keep your pH in the mid 7s, that's what's good for your new finish.
And because your pool is new, and possibly because you have high TA in your fill water, pH is going to be a constant battle for a while. Maybe a year, maybe indefinitely. That's how my pool is. I'm well past the one-year new-finish break-in period, but I still have to add acid constantly because of the TA in my fill water. Oh well. That's why I automated acid injection, so I don't have to deal with pH every few days. I decided to add the system early on, regardless if I later found out my pH would stabilize once the new plaster was done being new. I figured it'd be nice to have, even if I didn't need it to inject every day, and I might as well get good use out of in in that first year, when for sure it was going to be needed. As it turns out, it's been a good investment, because it's been four years now, and my pool still drinks a lot of acid.
Anywho, just some extra info for you. Hope it helps...