How much evaporation do you get with your cover?

[CASwede]

I recently added a 12 mil bubble wrap pool cover to our pool. There are a couple of small gaps, probably under 7 or 8 square feet total. It's regularly in the 80's here, with very low humidity. I'm still losing about half an inch of water or so a day, or more. Could the minimal uncovered portion cause this? I can actually hear the pool gassing off around the edge when the sun hits it direct. The pool water is about 83 degrees, and is rooftop solar heated.

I'm fairly sure I don't have a leak, as I only had to add water once a month or so in winter.

FYI, the reason for the gaps in my coverage is because I had to flip the cover. I cut it to fit with the bubbles up. One day I noticed a bright sheet on the cover, and realized water was all over the top of the cover around the bubbles. I had basically created a nice warm bed to speed up the evaporation! The evaporation has gone down significantly with the cover the correct side down, but I'd like to hear how much other people lose.

 

[Bama Rambler]

Have you performed a bucket test to make sure it's not a small leak?

You didn't say where you were located, but I highly doubt 7 or 8 sqft would allow that much evaporation.

 

[CASwede]

Did the bucket test twice. Both times I came home to a floating bucket, so water was leaving the bucket faster than the pool.

I also did the dye test around the skimmer, light, and drain. Nothing.

Humidity here in the east bay valley of the san francisco bay area is usually around 30%, with temps around 90F. I think we are just subject to massive evaporation. The bubble wrap cover has two 5" seams that dip below water level and run the length of the pool. Even with the pump off I can see the very hot water moving along those seams in a current. I expect its working like an efficient evaporation pond.

I measured water loss, and its about 1/4 to 1/2 inch per day. My first pool, so i guess that is normal here.

 

[Bama Rambler]

It's most likely normal. Next time you run the bucket test, fill the bucket a little higher than the pool. The effect will be the same and the bucket won't float away.