Cracked Acrylic Shell - Leaching Brown Substance

[pnw_1987]

Hi all,

 

I recently moved into an older home with a sunroom that contained a 1986 Beachcomber in-ground hot tub with an acrylic shell over what I believe to be fiberglass.

The shell had a bunch of cracks that were leaking a brown/tan substance with the consistency and color of maple syrup.

I let the tub dry out for a few weeks until the leaking stopped and then covered the cracks up with plast-aid then sanded it. It seemed to have stopped the leaks.

After filling up the tub for the first time a noticed a few more very small cracks that were slowly leaking the same substance, so I must have missed a few areas. I will empty the tub soon and repair those leaks in the same way.

I am wondering if anyone knows what that substance is and whether it may be toxic or harmful. I want to continue using the tub for a few more days before I dry it out. I did get some advice to ignore those cracks and the oozing substance, since they don't impact the water-tightness of the tub, but I ignored that since I was concerned about whether the substance was potentially toxic. It doesn't seem like the substance is dissolving in the water, as I can see and touch the substance on the tub shell.

Thanks in advance.

 

 

 

[ratchett]

God, in-ground hot tubs were such a popular thing and people still try to do it - but it's dumb because it's much harder to access all four sides of the spa if/when something needs to be serviced or replaced (like a jet nozzle or something).

Sounds like that shell is wearing out and those cracks are due to stress from holding water and running all these years.   At some point you'll need to throw in the towel and replace the tub.

22 hours ago, pnw_1987 said:

I am wondering if anyone knows what that substance is and whether it may be toxic or harmful. I want to continue using the tub for a few more days before I dry it out. I did get some advice to ignore those cracks and the oozing substance, since they don't impact the water-tightness of the tub, but I ignored that since I was concerned about whether the substance was potentially toxic. It doesn't seem like the substance is dissolving in the water, as I can see and touch the substance on the tub shell.

Very likely this is biofilm scum.

When a hot tub is used regularly, a thin layer of microorganisms can build up on the surface, and this is called biofilm. Biofilm is a mixture of bacteria, fungi, and other tiny organisms, along with their secretions and waste products. Over time, biofilm can accumulate and form a scummy layer on the walls and surfaces of your hot tub. This scum is not only unsightly, but it can also harbor harmful bacteria that can cause skin infections or other health problems. To prevent the buildup of biofilm, it's important to regularly clean and maintain your hot tub, and to use the appropriate chemicals to keep the water clean and balanced.

The cracks in your shell have created essentially the perfect environment for biofilm to fester/grow.   A purge product like AhhSome could be used to dissolve this biofilm scum (Unlike the directions, you would need to extensively purge - run jets for 20 minutes, then off for 10 while you clean scum at water line, run jets AGAIN for 20, then off while you clean fresh scum at water line, repeat a dozen+ times until nothing fresh settles at the scum line).

If you purge before every drain/refill you might get a few more years out of that shell, but it's certainly time to consider an upgrade. I believe Bullfrog Spas still sells a "spa vault" designed for in-ground installation, but I don't know of any other brands offering similar in-ground options.

[pnw_1987]

Thanks for the reply!

Yes, the tub is old and probably needs to be replaced; however, it cannot be easily done as the sunroom doesn't have a door large enough to bring a new tub in. I am going to try to see how much life I can get out of this shell. 

It is possible that the substance is bacteria, but it smells more chemically than bacterial. I suspect it has something to do with the chlorine reacting with the adhesive used to attach the acrylic to the fiberglass, but I have no idea what sort of nasty chemicals it could contain.

 

[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.

[CanadianSpaTech]

If water gets below the acrylic and pools over time the hardness/mineral in the water can "rust" and ooze out brown stuff. Usually see it when there is a bubble in the acrylic and then the bubble opens. Just my take on it.