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04/06/2023 04:08PM  
I'm testing my Marmot Limelight 3P (2019 version) Tents rain proofness. Overnight and today 2.5" of rain so far, mostly steady, but a few downpours. This, of course, is a test of the rainfly and after 2.5" the inside portion of the rainfly is now completely holding a very thin layer of water moisture on the inside of the rainfly material that is over the tent floor area. The moisture layer is slightly beading but with no noticeable drops ready to drip off onto the tent floor. Although there are a few places with water on the tent floor. Probably about a thimble or two volume of water on the floor. The vestibule areas of the rain fly are much worse than that of the rainfly area over the floor. It seems that some of the water on the tent floor is coming from the vestibule flapping a bit in the wind. I don't recall this ever happening before. Last season I did wash the rainfly and retreat it with NIKWAX products when I applied new rainproofing, I did use way more than the manufacturers recommendation only because it's hard to judge the application rate with a spray bottle. but you wipe most of the stuff off anyway. As a note, the rainfly seams are not leaking it's like the rainfly is just saturated throughout. Any suggestions on how to fix the rainfly?
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04/06/2023 05:10PM  
Is it wet because the fabric is saturated, or because it's raining so hard it's beating the water through? Or, is it wet on the inside because of condensation?
2" is a lot of moisture to wring from the atmosphere, I think I would be hard pressed to keep my stuff from getting a touch damp if that much rain fell when I was camping.
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04/06/2023 06:05PM  
The moisture on the underside of the rainfly is likely condensation caused when the rainfly temperature drops to at or below the dew point. This causes the moisture in the relatively warmer air under the rainfly to convert from water vapor to water droplets when it contacts the cooler rainfly. Conditions have to be favorable for condensation to form so you may not have noticed this before.

Condensation is usually not a concern with double wall tents because the interior canopy places a barrier between the occupants and the rainfly and the water droplets tend to run down the underside of the rainfly onto the ground. I use single wall tents and when I am concerned about condensation and dew point temperatures I do my best to control the inside moisture and temperature.
04/06/2023 06:49PM  
Probably condensation. The vestibules are worse because the moisture from the ground is not blocked there. Try it again sometime when there's no rain, and hose it down thoroughly to see if it leaks through.
04/06/2023 09:11PM  
Thanks for all the replies. Condensation seems to be the answer and as it was in the mid 40's during the day. I did forget to mention that although the rainfly is so wet water still does bead up into puddles on top of the fly and then rolls off when the puddle gets big enough. You can tell which parts of the fly get saturated by the darker shade of color in those areas. In between showers it does dry out quickly in 100% humidity just with the breeze which seems consistent with the condensation explanation. Apparently, we're due for much more rain tonight.
04/10/2023 12:48PM  
My buddy's tent last fall would allow a puddle to form and remain in the center of the top of the fly. Enough rain would eventually cause condensation to form and then gravity would pull the condensation to the low point where the moisture would then contact the inner tent mesh and drip through. I remember waking up one night to my quilt a little damp from that. I'm sure minor amounts of moisture also came through the fly due to saturation from the puddle.

The next day I redid the guy lines on his tent and we had no sag issues the rest of the trip. Sometimes it's just about knowing or experiencing how your gear performs.
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