I had to make a small repair to our spa cover, because the surface had been punctured by a fallen tree branch and there was a small hole, and I didn't want rain water to soak into it. So I was told that this could be easily done by unzipping the cover and removing the styrofoam filler, and then I'd have clear access to the vinyl which could be patched.

Anyway, when I opened up the cover and began removing the foam section, the entire inside of the cover was coated in a gross, gooey slime! Remember the movie Ghostbusters? It was just like that! And just out of curiosity, I opened up the other section, and the same thing. Has anybody else experienced this? What could be causing it?

I've since allowed the cover to completely dry out. The small hole has been patched, and the styrofoam pieces have been put back into place. But whatever that slime was, it's sure to come back once the cover is exposed to the moisture from the tub. I'm concerned that the slime may leach out through the little vent holes and into the spa water. Although I've never previously had any problems with the water itself or any visible sliminess in the water or on the tub surface. BTW this spa cover is only about 6 months old.

Any thoughts?

Slime bacteria ?

Perhaps the cover was somewhere punctured before , moisture seeped in and developed slime bacteria ?

Disinfect it and let it dry - re-inspect it after a few weeks and please keep us posted

I had same problem. my cover has a little "breather or weep " hole in the inside of the cover. I had slime inside and smelled really bad, musty, moldy smell. I removed the styrofoam core on both sides and scrubbed the inside and outside of cover, I used a mix of clorox and water in a spray bottle. hosed it all down and let it dry in the sun, and even turned the cover inside out and did the same thing. sprayed the styrofoam also ,wiped them down, and let them dry in the sun. made a big difference. smell and slime gone .

Yup I have that small breather hole on the inside of my cover as well.

Even after repairing the small puncture, and thoroughly cleaning and drying out the styrofoam core and the cover itself, water is getting inside via this breather hole, and also seeps in through the seams, and eventually will water-log the foam. The problem is already starting all over for me.
After spending nearly $800 on this new cover, I'm thinking it will not even last me through the next winter.

Does anybody make a good cover that's water tight on the inside?

The styrofoam inserts should be covered in plastic - if that plastic is compromised then the styrofoam will wick up the water. When I run into this I pull out the inserts and inspect the plastic, then sealing it real good with shipping tape.

You could do as we do and add one of those blue "bubble wrap" plastic solar blankets between the water and the cover. It seems to reduce our cover absorbing moisture and getting heavy.

That's a very interesting idea, Denny.

Does the bubble blanket just sit loose over the spa? Does it sit on top of the water (like it would for a swimming pool), or does it sit on top of the shell edge? And then the spa cover sits on top of that? How does it perform in the winter?

I think this would be a relatively inexpensive solution for me, and sure beats having to shell out for a new cover less than a year after buying this one. Maybe you have a photo of how you do this?

Funny thing about the water absorption....I now have water collecting in the flaps that hang down the sides of my cover. I think as the water collects inside the cover, it travels to the edges, and then seeps through the seams and into the flaps. They're full of water, and when I squeeze the flaps, the water squirts out of the bottom seam. I'm thinking this is going to create a huge problem come winter, since the flaps are on the outside and the water will definitely freeze and not have a chance to drain away (or be squeezed away).

hmmmm...maybe this thread should have been placed under the spa cover section, since it seems to be a problem with my cover that's creating the water problems.

It hangs out over the sides a little bit. First time I used on I cut it to float on the water but it always gets bunched up when the spa comes on the automatic times. I fold it up with the cover when using the tub. It really helps keep the moisture out of the cover. About $25 at most spa stores.