which cover to get to slow FC loss

[beezar]

Was going to buy a cover for my spa to slow FC loss when I go on a week vacation for a month. Is a black solar cover (the one with the bubbles) ok, or should I get something else? Will black slow loss more than blue or clear?

Also, I have a freeform spa, and was wondering if I can cut one of those covers with scissors to the shape I want (never seen a solar cover, so not sure).

 

[Bama Rambler]

You can cut it with a stout pair of scissors. or a sharp knife. I have clear and it doesn't affect the FC loss that I can tell. I would go with a black cover if slowing FC loss was my goal.

 

[chem geek]

It's not so much the color that matters, but the opacity. If light does not shine through it, then that will prevent the FC from breaking down. A black cover will absorb light and tend to heat the surface of the pool which with circulation can provide some heating to the pool whereas a white cover would reflect the light and tend to prevent the pool from getting warmer from the sun so might be more useful in a place like Arizona to prevent evaporation, but to keep the pool from getting too hot too quickly.

The clear and blue covers still let light through (the blue somewhat less than the clear). Again, get something that you cannot see through. Hold it up to a light or the sun and if you can't see the light at all or it's very dim then that's the best. The electric automatic safety cover on my own pool is mostly opaque, but does let a little bit of light through. Mostly though, it cuts down the FC loss significantly.