Originally Posted by rbrain
Compressed air contains some moisture due to the nature of condensing air. That is why on the bottom of compressor tanks there is a drain valve to clear the tanks of water. I don't use mine because I don't want to get moisture in my tubes (albeit it's a small amount of moisture). May not be a big deal...
The water vapor is present regardless of the air being compressed or not - it just precipitates out when compressed. That same water vapor is getting pumped into your boat with a hand or foot pump, you just don't see it. If the raft tubes were clear, we would see all the condensation on the inside of our boats forming when tubes warmed by sun come in contact with cold water - just like on our frosty beverages. So...I tend to think its more of a liability thing for tards incorrectly/over inflating boats than something that is bad for the raft/cat structure.