Last week I went to an indoor pool, which was being taken care of by the customer, or at least one of the customer's employees. The pool was a small fiberglass pool with a treadmill in it. It was right on the line between a big hottub and a small pool. About 8'x16'x4'. They had a problem with algae growing on the walls of the pool, so they called me. The filtration system is basically a hot tub setup. A small cartridge filter, and a second pump to run the jets.
When I tested the chemistry (using test strips) the chemistry was off the charts low, with the exception of hardness. I shocked the pool, and ran the jets to circulate the water. I tested several times to make sure the Chlorine level was high enough. Then I started working on the pH. I added 4 lbs of ph+ (4lb is usually too much for a 20x40), ran the jets, and tested several times in different locations. The pH was still off the charts low. I added more slowly, testing repeatedly in different locations until I finally saw a slight change on the test strip. I let it run for a while testing every few minutes to see if it was changing. It didn't change, so I added more. Eventually I got the pH up to where I wanted it, so I let the jets run, and continued to test periodically, watching for changes. It seemed to finally be stabilized.
So my questions are:
What would cause pH to get so low it would take this much pH+ to bring it back in an indoor pool?
Was I right to assume that I could watch the pH come up as I waited? I realize that doesn't really work in a full size pool.
How likely is it that the pH would continue to rise once I stopped adding.
When I added the pH+ the water turned cloudy instantly. Is this an indication that I added too much, or is it likely a result of other conditions such as algae or bacteria dieing, or precipitation of Calcium?