My pool is still covered. About a week ago I tested the water, PH was 7.6-7.7. Now PH is 7.2 at best. I added maybe 1ft of water (don't remmeber if pool water was added before or after I did the test) and had pump running for a few hours. No chemicals were added. Alkalinity hasn't changed much, now it's 110-120
I never had PH drop before, it always rises. Any idea what can be the reason? I'm planning on opening pool today, but I can see the water is pretty bad, I see some brownish foam in the skimmer. I did very bad job last closing - didn't add algaecide and didn't shock (had issues with algaecide turning into ammonia previously. had 0 issues with pool last year, so decided not to shock and closed with FC level around 7.5, but it went to 4-5 in 5 days while was covered)
EDIT Removed the cover, added chlorine to bring to shock level. Tested in about an hour, less than 1. Tested CYA and sure enough it went down from 30 to nothing. I tested it last week and it was 30. I didn't retest it today, because I assumed it's still 30.... In less than a week from 30 to nothing while the pool was still covered. Why would it happen?
I bought stabilizer and already have socks in skimmers and on return.
Question - With CYA 0 what kills chlorine more, the sun or the algae? Should I be adding chlorine now or should I wait until dusk? (don't want to waste another ~~$15 if sun is killing it right away)