I've a 5-year old waterlogged cover. I slit the polyvinyl wrapping and drained out about 20 gallons or so of water, and am able to continue using the old cover (for now). I don't like the economics of replacing it every 5 years. I'm trying to understand this situation:
- Do all covers wrap the styrofoam in the inner layer of clear polyvinyl as the one in my spa that trapped so much water?
- Can anything be done to prevent water from permeating into the wrapper and getting trapped - for example, lowered level of water?
- My spa has a waterfall that runs when the spa purges - I'm thinking this might be throwing water against the underside of the spa cover and wondering if that contributes to a problem, and wondering if I shouldn't disable the waterfall.
- What is the expected life time of a spa cover?

Thank you.

5 years is a decent life for a spa cover.

If the foam wasn't wrapped in something, the cover would last about 6 months before the foam soaked up enough water to weight hundreds of pounds

If you were able to actually drain the water out, it sounds like you either had a defective cover, or it has a hole in it.


From rhtubs.com Spa Cover FAQ;

Why do some spa covers get so heavy as they get older?

The foam a cover's cores are made of is called Expanded Polystyrene and is made of small beads that are expanded with steam. Once expanded they are dried and then "attached together" simply by compressing them. The more pressure they are compressed under, the high the density of the foam. The individual "beads" are waterproof! HOWEVER, water can saturate between the beads.

To prevent (actually reduce) water absorption, the foam cores are "sealed" in polyethylene. The method used to seal the polyethylene is an important factor. Many cheep covers simply have the polyethylene taped closed. Not good, as the tape will eventually fail. Better covers have the polyethylene heat sealed. While this is usually better than tape, if not done carefully and properly it can actually be worse. When the polyethylene is heat sealed, if it's over heated the seam will be excessively brittle and can crack, allowing water to enter the foam.

The most obvious cause of water absorption would be a small hole punctured through the cover. Even the smallest hole will allow a large amount of water to enter the foam over time.

The most common cause of water absorption is the "natural degradation of the polyethylene". Over time, chlorine, bromine, non-chlorine shock and ozone will break down the polyethylene causing it to become porous. The thicker the polyethylene (we use a 6 mil thick polyethylene), the longer it will resist this chemical degradation. At some point however, it will become porous enough to allow evaporation and steam to penetrate through it. It WILL NOT be porous enough to allow the steam that has condensed back into water to drip back out.

Since eliminating all the chemicals isn't possible (and still have a safe spa) the best preventative measure is a floating blanket. The blanket will greatly reduce both chemical off gassing, and more importantly evaporation. It's also important to completely remove the cover for a minimum of 20 minutes when shocking the water. This will allow the off-gassing chemicals to freely escape without penetrating into the cover itself.