How much muriatic acid will I need each week with a SWCG? Let's do real maths here.

[AUSpool]

...pH in the high 8 range...

??? Is that a typo? High 8's, thats high.

Back to the OP and for me acid demand or use is about where your pool wants settle at and what target you want to choose. My pool stays at 7.8 for long periods of time, if I were to force it to 7.6 I would use loads of acid but if I leave it at 7.8 I use no acid at all. For me though acid demand is more for alkalinity control rather than pH with larger doses needed from time to time to lower my TA in summer when my evaporation is out of control and my TA creeps up from the TA in the top water. Odd, but its kind of similar but reverse of the reef aquarium where I'd manage TA to indirectly manage pH.

 

[Esloser]

I go through about a gallon a week. It's a plaster pool that is still relatively new. I usually go to the pool store and get a box of 4 gallons and don't let them sell me anything else. I'm good for about a month. When I test my water and it's above 8, I add about 1/2 a gallon and test the next day. It's usually down in the 7.6 range and by the time I test again in a few days it's back up around 8 so I add another 1/2 gallon. Sometimes, I feel like I am the only person on the forum who isn't using measuring cups.