Does water affect line tension?I’ve heard conflicting theories about what water (from rain, from wet feet, etc) does to standing tension of a slackline. Mostly these theories look at nylon lines, which are hydrophilic (meaning they easily soak up water). Polyester is hydrophobic, so there is less concern there, as it’s difficult to saturate polyester with water. We know that water probably doesn’t help break strength, so you should avoid getting any very tight line wet, but it would be nice to know what the water will do to the tension. Does it rise? Does it fall? Most people, in my experience, seem to think it rises. My personal experience, from walking a lot of dry waterlines that eventually get wet, tells me that it falls. Let’s do a test!
Cliff notes: if you don’t want to watch the video, the tension does indeed fall, from 1100lbs to 925lbs. This was a 56.5′ line with a standing (read: settled) tension of 1100lbs, and it experienced a drop of almost 20% of its tension. Line length, tension, the amount of water, the humidity, and probably some other factors will all affect how much tension falls, but I think this experiment strongly suggests tension will likely fall in most if not all cases.