I have a five or six year old Leisure Bay hot tub with a 36” plus hair line crack leaking from the underside. The best I can tell it’s an acrylic shell with fiberglass base, then a thin coating of “semi-hard” black insulating foam. I can handle the glass work but, my main questions are what is this black undercoating and how do I reapply it, where do I get it? Added info The crack is running almost the entire length of the lounger at arm rest level. The crack is not visable from the top. Although the crack is long there's only a light drip.





Thanks, Mike

Hi Mike,
The backing is called "Black Diamond", and is a foam composite.
The acrylic shell is backed with a thin white sheet of thermal plastic
to add R value. Repair will entail a "Bondo" like repair on the backing,
with an acrylic surface repair.
Some shells came with a non-transferable lifetime warranty if you are the orriginal owner.