Army Issue Bivvy Bag and Rain Ingress?

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Chief

Member
Dec 18, 2019
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Lincs.
Hi,
A while back I bought an ex-army issue bivvy bag. I had only used it once before in summer weather, so recently I bought the two Nikwax products and washed/re-vitalised the goretex.

Tonight hoping to see the super moon I tried sleeping outside in it (no tarp), needless to say it promptly decided to rain and the moon remained out of sight.

Now, I was feeling dry and comfortable inside it, but after the rain stopped I felt the inside of the bag, and found the inside material to be damp to the touch (left my fingers slightly wet), with some areas of my sleeping bag likewise affected.

So I just wondered if this was normal or not, whether it was like tent fabric where water can seep in if somethings touching it or not? It may have been near the taped seam so I realise it may be the cause, but I thought others may know if this would be the norm. for this form of bivvy bag.

Just to add, I was only out there 90 minutes so definitely no condensation build up, in the end it was the light pollution and traffic noise that finally got to me give up and go in for a quiet night :)

Thanks.
 
Apr 8, 2009
1,122
102
Ashdown Forest
If you have ruled out the condensation factor, then unfortunately you might need to consider a breakdown in the goretex membrane itself. Remember that in service these bivvy bags may have had a hard life and not be particularly well cared for. I forget the number of times i was compelled to use a bivvy bag in the midst of a gorse thicket or laying on brambles, with the thorns spearing through the fabric left right and centre. Re-proofing will only help to an extent, but will never render a perforated membrane fully water tight again. A microporus membrane like goretex should not wick water through it when touched (i.e. unlike canvas), but it does still have a hydrostatic head - given enough pressure, water can be forced through the membrane, even if it is in good condition. This might manifest on a bivvy bag e.g. if you are lying direct on a very wet surface, or water puddles underneath you (e.g. on top of your roll mat between it and your bivvy bag).
 
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Erbswurst

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Mar 5, 2018
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Dry it, tuck it in your bath while keeping the entrance high, turn it inside out and you will see the holes, because you get whet spots.

These you can glew somehow with seam sealer.
 
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TLM

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Nov 16, 2019
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Goretex works by allowing water (gas) out and not water (liquid) in. For this to work the bivvy fabric needs to have it's DWR in working order, otherwise the gas does not get out. So my guess is that it was condensation.
 

Chief

Member
Dec 18, 2019
19
8
36
Lincs.
Thanks for the replies.

Just to add to my orignal post I was face down to the ground with the hood of the bivvy bag on the ground (something I regretted when it started raining since it would have been much easier if it had been on top!).

The taped seam which seems very well glued still on inspection (now the bag is dry again) was running along the length of my back in direct contact with the downpour. The damp area was all around my lower back and down one side.

Although the roll mat (it's about twice the size of the bivvy bag) was getting wet, it only had a sheen of water to it and everything had been put out while it was dry and not raining so I wasn't lying with it directly on any puddle but it was wet round me.

I guess it was possible water could have been pooling in the small of my back (with two sleeping bags + liner + clothes I couldn't feel anything).

It was only when I checked with my hand as a precaution since it was the first time out in the rain to check everything was still keeping dry that I felt wet material and my hand got wet.

No bath unfortunately, but will it work just as well to shower the outside and then check inside? or does it need submerging in water for best test effectiveness?

Thanks.
 

Erbswurst

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Mar 5, 2018
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Pull it step by step slowly through the kitchen sink!

Just the shower could not be enough.
 

Erbswurst

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Mar 5, 2018
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I recommend to use the equipment in intended use, not upside down and inside out or whatever you can find in YouTube videos.

The intended use of a British army bivvy bag is to put it as a second skin over the sleeping bag and to pull the draw string tight if needed, then roll onto the side, together with sleeping bag and bivvy bag, and form some kind of roof over the nose while you breath outside.

If trapped in storm you can roll so far that your body and nose point into a 45 ° angle to the ground, on the leeward side of course.

The insulation mat that is issued with the bivvy bag is 190 x 60 cm.
If you take a larger one you create a nice garden pond and don't need to wonder why you get whet in the bivvy bag.
It isn't meant to sleep in a garden pond.

 
Last edited:

lostplanet

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Aug 18, 2005
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Kent
ive been having the same problem, It could be a dodgy bag. Im .
looking at getting a brand new one and try and do a back to back.

 

Erbswurst

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Mar 5, 2018
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It's possible that someone didn't rinse it well enough after washing it.

If there stays detergent in the membrane it doesn't work.
 

MrEd

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Feb 18, 2010
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www.thetimechamber.co.uk
Thanks for the replies.

Just to add to my orignal post I was face down to the ground with the hood of the bivvy bag on the ground (something I regretted when it started raining since it would have been much easier if it had been on top!).

The taped seam which seems very well glued still on inspection (now the bag is dry again) was running along the length of my back in direct contact with the downpour. The damp area was all around my lower back and down one side.

Although the roll mat (it's about twice the size of the bivvy bag) was getting wet, it only had a sheen of water to it and everything had been put out while it was dry and not raining so I wasn't lying with it directly on any puddle but it was wet round me.

I guess it was possible water could have been pooling in the small of my back (with two sleeping bags + liner + clothes I couldn't feel anything).

It was only when I checked with my hand as a precaution since it was the first time out in the rain to check everything was still keeping dry that I felt wet material and my hand got wet.

No bath unfortunately, but will it work just as well to shower the outside and then check inside? or does it need submerging in water for best test effectiveness?

Thanks.

ruen it inside out and fill it up a third of whatever in the shower then hold it up I bet you will see pinholes letting water through.

mine did exactly as you were describing and all of the foot box and the back area where you back would be had lots of pinholes.
I used goretex iron tape and seam sealer to repair it, and it’s improved it a good 90%

all my bivi bags that are goretex have done it to a greater or lesser degree - condensation is a problem sometimes particularly if I get in the bag ‘hot’ and the outside temperature drops some time later.

I almost always use a Tarp with my bivi - mainly so I have an admin area if it’s raining. Last weekend I slept out in my Dutch bivi only and no tarp and was fine - no condensation at all, although I did not have the face part zipped up
 

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