A few experiences with my solar cover:First month the outdoor temperatures were nice, we had the pool cover on all time except when in use for a few hours a day. Now that we are hitting 90+ during the day, I have found that if I keep the cover on during the day, the water will get very warm but algae will start appearing. Is it fair to state, keep cover off during the day during hot humid summer (Washington DC area)
1) My PH would drop if the cover was left on all the time (after about 5 days or so), but removing it for a few days would naturally allow the PH to come back to a normal range. I added no SODA ASH or BORAX.
2) My cover fit perfectly over the pool in 2 large sections, and one very small section for the steps. Same type of event (if left on for days), algae spots would appear. There have been members reporting that my chemicals were off (not a chance), and that it is my chemistry that was causing this (again - NOT a chance). Eventually I cut 1' off the covers around the 2 pieces and this year, no matter what, there is no algae. The only disadvantage to cutting the cover is that you have some heat loss during the evening. Last year, at night (real cold nights) the water temperature would drop 2* at most. Now I am seeing a 3* drop with the way the cover is cut.
3) My cover goes on at night (and comes off early a.m.), now given that the temperatures will be soaring and we are heading into hot weather, at least for the east coast. I find that having the cover off during the day is a good thing. Another thing that I have done (or doing) is that I manually turn the filter on for one hour (as I never now when the cover will come off). The surface water, which of course is warmer due to the solar cover is picked up quickly by the skimmers (faster than evaporation), at least I believe and pushed towards the middle and bottom of the pool, allowing other water to naturally heat up.
Solar covers do work, but can be annoying when removing and having to bend down. I have to pull from both sides not to crease them. My next go around, the new cover will go into 3 pieces (about 12' each), instead of 16', which will make removing a lot easier. When I put on the pool, I carefully place in water and use the brush to roll it out given the PVC is on the inside. Then the PVC is used to make sure the cover does not blow off the pool.