So why do hot tub covers get so heavy over time?

AGP Company , San Antonio, Tx

The simple answer is that the hot tub cover foam core becomes waterlogged over time. This water soaks the core and is what is responsible for most of the weight.
When this happens, you hot tub cover will become very heavy and your cover will no longer be as effective at protecting your hot tub from the elements.
There are two main causes of a water logged foam core:
1. Poor Water Chemistry – If your water chemistry is not balanced properly it can become very corrosive. Over time this corrosiveness will disintegrate the vapor barrier around the foam cores allowing water to pass to the core soaking it over time.
2. Broken Cover – If there is a crack in your cover, water can enter the cover causing the foam core to become completely saturated over time. The foam core itself can also become broken if someone sits on the cover often penetrating the vapor barrier as well allowing water to enter the cover soaking the core.
While you can just ignore the problem and keep using the cover, a heavy cover that has been saturated from water will not protect your hot tub properly and will drastically impact the cost of running your hot tub. If you find your cover is getting heavy, it is best to address the problem right away.