uh2

I found this thread while searching for a new hot tub to buy for a house we recently purchased. I signed up on this forum JUST to reply to you @pnw_1987. Our house has an older recessed tub in it...manufacturer unknown. Previous owners probably never used it over the last few decades. I cleaned it out with ahhsom, filled it up with water and fired it up for a family get-together over the July 4th holiday. It has a disclosed leak somewhere....unfortunately the tub is partially recessed into a deck and is about 12" or so away from the house on two sides. Regardless, after loading it up with water and having family in and out of it for a week (and topping it off with water every morning) I dumped the water out and shut it down permanently. Before we used it, I noticed small hairline cracks in the shell. I patched those before filling it with water. After I shut it down, more cracks appeared and they started to ooze the same brown substance you have. @ratchettis right, it appears that the shell was stressed due to age and inactivity and when the weight of all that water plus humans after YEARS of not having either was added to the mix, the shell just started to fail. I don't believe that brown substance is bacteria. I believe it is a reaction to chlorine by the fiberglass underneath the surface (which has now failed). Just wanted to chime in and let you know you're not alone.