I'm trying to help a friend out with his pool.
The pool is in a heavily wooded area in southern Oregon. Over the winter and during the spring he really let it go with leaves and needles from the trees settling on the bottom of the pool. And then when the weather got warm it turned really green and nasty.
Anyway, when we started in early June the readings on this 19000 gal vinyl liner pool were pH 6.8-, FC 0, Alk 40, cya <20, Calcium 120, TDS 800.
I started by getting the FC up to 15 ppm with bleach at the same time as using tri-chlor to raise the stabilizer level a bit. It took 4 high doses of bleach before we started getting a FC reading. We added 6 lbs of sodium carbonate to raise the pH.
We also added about 4 lbs of sodium bicarbonate to help with the alkalinity. We brushed and vacuumed and scooped and cleaned the filter and now the pool looks great, crystal clear.
What I'm curious about is the pH. Last week it was 7.3 with an alk of 100 and FC of 3 ppm. I expected it to rise a bit with the continued addition of bleach. This week it is 6.8 with an alk of 90 and FC of 10.5 ppm. The cya is just a little more than 20 ppm (melamine turbitity test). He was adding about 96 oz of 6% bleach every day last week. We aren't using the tri-chlor anymore.
Can you think of anything that would be driving the pH down?