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Bottom line, your choice. The Top Leading manufacturers seem to be all solid foam filled, I guess the others are cheaper then because they didn't spend the money to do it to their spa, does that make their spa better, cheaper or more costly to retain heat?
Well, I'm certainly not a hot tub manufacturer, but here is my guess...What they all have in common, though, is they try and make a heated air space to keep things warm/hot. -Ed
Question I have is when you want to get air mixed into the water were does that air come from? If it's from inside the heated space then cold outside air must be allowed inside to makeup the lost air otherwise there would soon be a vacumn created.
Why then do manufacturers have a warranty exclusion for temperatures outside of the range of 34° and 104°? :-/ Obviously, 32° is when ice begins to form? To me, that means if I lose power in the winter and something freezes, it is not covered by the warranty, even if power was lost because of a warranty failure?