Wow 4 gallons of acid, that seems very excessive. Not sure why they would add that much unless the PH was SUPER high. I have a pebble tec finish so I'm not sure what is all required for plaster. Usually you put acid in a quart or two at a time to reduce your PH.

You usually don't need to worry about adding chlorine or stabalizer if you water temperature is cold which is usually under 55 or 50 degrees.

So anyways I'm kind of at a loss as to why so much acid was needed.

Eric