Periodically I change the water in my spa, using tap water. I then put 2 bromine tablets in the filter and let the pump run for a few hours while it heats (220 VAC) up the water. When I check the pH, it is very high, so I use dry acid (pH down) to bring the pH down to 7.4. The next day I check the pH, and even though nobody has used the spa the pH is very high again. This will keep happening for 10 days or so, then the pH will stabilize. I've thought about adding stabilizer (cynauric acid) to stabilize the pH, but been told that this will work only with chlorine levels. So why does is take so many days to stabilize the pH level? What can I do to have it stabilize right away?
Thanks, Bill