How to keep tent floor dry?

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pjclinch
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Re: How to keep tent floor dry?

Post by pjclinch »

irc wrote: 30 Sep 2022, 12:35am I appreciate Vaude tents cost more than Argos tents but I imagine both were made in far eastern factories and would have similar ways to be less than perfect.
It's not about whether it was made in China, it's about the QA regime specified for the production. Chinese factories are quite capable of making space probes that can go to the moon if the QA regime is sufficiently high, so I think we can assume they can also make a waterproof groundsheet.
The thing is tighter QA costs more money, and people don't like to spend more than they have to. I imagine Vau De are willing to spend a bit more than ACME Bargain Tents! Inc. acting for Poundshop and contracting the same factory.

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Re: How to keep tent floor dry?

Post by pjclinch »

Galactic wrote: 28 Sep 2022, 3:23pm
Definitely seepage from below rather than condensation - the floor fails your bucket test
If it fails the bucket test then it's a duffer, whether that's from accumulated wear and tear (in which case you need it replaced at your own cost) or faulty manufacture (in which case it should be replaced by the seller).

On to condensation...
Tent fabrics will have a stated hydrostatic head figure, well in excess of a meter for groundsheets, which means the fabric will withstand water of a column over a meter high. Bear in mind that a fairly flimsy carrier bag (assuming no holes) can pass the bucket test and you can see that "waterproof" isn't actually that big an ask... but that same carrier bag can give us some insight as to how much condensation can be an issue. Put something cold and wet in your bag (a trip to the fishmonger shows this perfectly) and even though the bag doesn't leak, the outside gets wet because you've got an excellent heat trap (the cold, wet thing that is an excellent conductor of heat), a good condensing surface (the bag) and typically quite moist air (in the atmosphere) all together.
And that's what tends to happen to tent floors when they're on cold, wet ground, and the thinner they are the more they suffer. You tend to get condensation [Edit to clarify: "obvious wet patches", you get condensation other places, but not in obvious wet patches] under pressure points (i.e., under mats, and under knees when kneeling) [Edit to clarify: think of the fine mist of droplets on a "steamed up" window, push a finger against it and you leave an obviously wet-looking spot].

I've never had a leak from the floor in any tent (variously classic Force 10s, Saunders and Hillebergs). I've quite often had wet floors from condensation, with the thinner floors more prone. Footprints help because even though they're thin it's insulation from the cold that causes moisture to condense out of the air.
But there are times when even with a fairly stout groundsheet and a footprint you'll get condensation, because physics. To eliminate condensation in lightweight tents, don't go camping...

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Last edited by pjclinch on 2 Oct 2022, 9:18am, edited 1 time in total.
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Cowsham
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Re: How to keep tent floor dry?

Post by Cowsham »

Maybe it's the internal size of the tent -- if it's too small I could see there could be a problem with condensation. I like my space and therefore have fairly big tents ie my trusty vango omega 350 is the stretched version of the 300 ( 3 man ) tent I think.

The lidl one I bought for my brother is sold as a 4 man tent but that's very optimistic even for aborigines.
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Re: How to keep tent floor dry?

Post by irc »

And that's what tends to happen to tent floors when they're on cold, wet ground, and the thinner they are the more they suffer. You tend to get condensation under pressure points (i.e., under mats, and under knees when kneeling).


Pete.
It is easy to tell condensation. It is gradual. Especially on the walls of the tent. If you crawl into a tent pitched on very wet ground and your knees are immediately damp that is not condensation.

Anyway it is easy for the OP to test this. Pitch on grass on top of a good waterproof sheet of some kind. Then remove the barrier. If you only get wet without the sheet it is seepage and not condensation.
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Re: How to keep tent floor dry?

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irc wrote: 1 Oct 2022, 6:36am
And that's what tends to happen to tent floors when they're on cold, wet ground, and the thinner they are the more they suffer. You tend to get condensation under pressure points (i.e., under mats, and under knees when kneeling).
It is easy to tell condensation. It is gradual. Especially on the walls of the tent. If you crawl into a tent pitched on very wet ground and your knees are immediately damp that is not condensation.

Anyway it is easy for the OP to test this. Pitch on grass on top of a good waterproof sheet of some kind. Then remove the barrier. If you only get wet without the sheet it is seepage and not condensation.
Not necessarily. The barrier may be thick enough to reduce rate of heat loss to the ground enough that moisture isn't condensing out of the air on the top side.
The bucket test - does a pool of liquid water drip through a suspended piece of the fabric - is one that will tell you if it's waterproof.

As for gradual... well yes, but for some values of gradual. Do the following experiment... get a thin plastic bag like a freezer bag and half-fill it with cold water. It shouldn't drip out the bottom because it's waterproof. Push gently anywhere around the water-filled bit and your hand will be a little damp, push gently at the top and it's dry. The harder you push the wetter your hand. This happens within seconds of filling the bag.

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Re: How to keep tent floor dry?

Post by irc »

If I am kneeling on a tent floor there is no air between my knee and the floor for water vapour to condense from. It is quite clear to me when my knee is getting wet from water coming through a tent floor within a few seconds of kneeling on it. But I guess we will just need to disagree on that.
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Re: How to keep tent floor dry?

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irc wrote: 1 Oct 2022, 3:42pm If I am kneeling on a tent floor there is no air between my knee and the floor for water vapour to condense from. It is quite clear to me when my knee is getting wet from water coming through a tent floor within a few seconds of kneeling on it. But I guess we will just need to disagree on that.
If you have a leaky floor your knee will get wet, but it can also get wet from condensation. There's no air between your knee and the groundsheet, but then there's no air between your hand and a water filled bag, yet you still get a wet hand. It's not the hand or knee causing the condensation, that's already there but it's a very fine film you typically can't see (heavy condensation is visible as droplets, but just because you can't see distinct droplets doesn't mean there's no water there). And the harder you push the more of that water you'll transfer to knee/hand, because the sheet (or bag) deforms to make more contact. The water's there already, so you'll get wet immediately.

Using a suspension test you can measure the amount of water before and after. If it's leaking then after half an hour there'll be a lot less. If it's not leaking, the bottom will very probably still be wet, but from condensation, though you'll have the same amount of test water where you put it.

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Re: How to keep tent floor dry?

Post by Galactic »

OP here again. While condensation is definitely an issue with the Vaude Taurus Ultralight (small space, not much in the way of ventilation, and no cross ventilation at all), this isn't what has been exercising me over the years. You know when water is coming from below when it rains so much the ground is really wet and it starts bubbling up through the groundsheet, or you even get a bit of a stream running through :shock:

As I said above, I'm rather taken with the idea of a shower curtain for this tent, and am looking around for a 3 person tent (for when I'm touring with another person). The decent Vaude models are now only a little cheaper than a Hilleberg Anjan, which has me counting up my farthings and ha'pennies to see if they might stretch that far, since I've heard nowt but good stuff about Hillebergs (might open a new thread on whether Hilleberg tents are worth the cost).
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Re: How to keep tent floor dry?

Post by pjclinch »

Galactic wrote: 2 Oct 2022, 6:10pm OP here again. While condensation is definitely an issue with the Vaude Taurus Ultralight (small space, not much in the way of ventilation, and no cross ventilation at all), this isn't what has been exercising me over the years. You know when water is coming from below when it rains so much the ground is really wet and it starts bubbling up through the groundsheet, or you even get a bit of a stream running through :shock:
That's a leak, and shower curtains/footprints etc. will only be so much use because any water getting between it and the groundsheet (and it will in boggy ground) will come through as soon as there's pressure.

So get a new groundsheet fitted (if not by Vau De, Scottish Mountain Gear have a good reputation for this, I imagine there may well be others) or replace the tent.
Galactic wrote: 2 Oct 2022, 6:10pm As I said above, I'm rather taken with the idea of a shower curtain for this tent, and am looking around for a 3 person tent (for when I'm touring with another person). The decent Vaude models are now only a little cheaper than a Hilleberg Anjan, which has me counting up my farthings and ha'pennies to see if they might stretch that far, since I've heard nowt but good stuff about Hillebergs (might open a new thread on whether Hilleberg tents are worth the cost).
We have 3 Hilles and consider them excellent, but you certainly don't need to spend that much on a tent to get a decent floor.
If you do get a Hille note that their 2 people tents really do fit two people and luggage. We do use a Kaitum 3 for 2, but it has slept 3 comfortably.

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Re: How to keep tent floor dry?

Post by ndmbike »

I like my lightweight tent(s).
The gossamer thin groundsheets are great for their poundage but they are thin.
I remember trying very hard not to 'say something' when a friend sat and kneeled on the groundsheet of my rather expensive quasar (£350 odd in the 90s) knowing that he was putting damage into the fabric. It leaked ever since that trip.
I try to spread the force of my bum, knees and feet using a foam mat and/or a thermarest.
Whatever you do, don't wash them with detergent. They lose any waterproofing they may have had.
If you want total waterproofing, you will need thick fabric and additional weight.
Having said that, pitching on damp ground is not a good idea, but it may be unavoidable and a 'bathtub' made from an old bivvy bag or a shower curtain is quite effective at directing the flood away.
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Re: How to keep tent floor dry?

Post by Slowroad »

I've also had two Vaude Taurus tents, neither have had damp issues till they were over 10 years old. I did use the manufacturer's footprints.
Hope you work out what the issue is!
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Re: How to keep tent floor dry?

Post by irc »

pjclinch wrote: 2 Oct 2022, 6:54pm
Galactic wrote: 2 Oct 2022, 6:10pm OP here again. While condensation is definitely an issue with the Vaude Taurus Ultralight (small space, not much in the way of ventilation, and no cross ventilation at all), this isn't what has been exercising me over the years. You know when water is coming from below when it rains so much the ground is really wet and it starts bubbling up through the groundsheet, or you even get a bit of a stream running through :shock:
That's a leak, and shower curtains/footprints etc. will only be so much use because any water getting between it and the groundsheet (and it will in boggy ground) will come through as soon as there's pressure.

So get a new groundsheet fitted (if not by Vau De, Scottish Mountain Gear have a good reputation for this, I imagine there may well be others) or replace the tent
Or alternatively spend £5 and try the shower curtain first.
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Re: How to keep tent floor dry?

Post by pjclinch »

irc wrote: 2 Oct 2022, 10:14pm
pjclinch wrote: 2 Oct 2022, 6:54pm
Galactic wrote: 2 Oct 2022, 6:10pm OP here again. While condensation is definitely an issue with the Vaude Taurus Ultralight (small space, not much in the way of ventilation, and no cross ventilation at all), this isn't what has been exercising me over the years. You know when water is coming from below when it rains so much the ground is really wet and it starts bubbling up through the groundsheet, or you even get a bit of a stream running through :shock:
That's a leak, and shower curtains/footprints etc. will only be so much use because any water getting between it and the groundsheet (and it will in boggy ground) will come through as soon as there's pressure.

So get a new groundsheet fitted (if not by Vau De, Scottish Mountain Gear have a good reputation for this, I imagine there may well be others) or replace the tent
Or alternatively spend £5 and try the shower curtain first.
Thing with the shower curtain is it will work fine in benign situations but come the time you actually really need a waterproof floor it'll demonstrate why tents tend to come with bathtub groundsheets, rather than just groundsheets...

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Re: How to keep tent floor dry?

Post by pjclinch »

ndmbike wrote: 2 Oct 2022, 8:20pm I like my lightweight tent(s).
The gossamer thin groundsheets are great for their poundage but they are thin.
I remember trying very hard not to 'say something' when a friend sat and kneeled on the groundsheet of my rather expensive quasar (£350 odd in the 90s) knowing that he was putting damage into the fabric. It leaked ever since that trip.
Blimey. If you can't kneel on a groundsheet without destroying the waterproofing then frankly it's not fit for purpose. I've never been that keen on Terra Nova stuff but frankly I'd expect better of a Quasar. Been kneeling in my Saunders and Hilles for years and the groundsheets are still fine.
ndmbike wrote: 2 Oct 2022, 8:20pm Whatever you do, don't wash them with detergent. They lose any waterproofing they may have had.
If you want total waterproofing, you will need thick fabric and additional weight.
Detergent doesn't destroy waterproofing. Detergent works by reducing surface tension of water droplets so they can more easily penetrate the weave of a fabric and thus clean it better, but if the weave is covered by an impermeable layer of polyurethane (which groundsheets typically are) then that's a moot point. I certainly wouldn't go out of my way to use detergent (plain water usually enough, if not then warm water, if not then a little pure soap), but it's not waterproofing Armageddon that many people seem to think it is.

For total waterproofing you just need something with sufficient hydrostatic head that water can't be forced through it by the pressures it's routinely subjected to. That can be remarkably thin, though very thin sheets are easier to wear the coating off so they don't last so long and as they have pretty much zero insulation value are very, very prone to condensation.

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Re: How to keep tent floor dry?

Post by PH »

pjclinch wrote: 3 Oct 2022, 7:47am
ndmbike wrote: 2 Oct 2022, 8:20pm I like my lightweight tent(s).
The gossamer thin groundsheets are great for their poundage but they are thin.
I remember trying very hard not to 'say something' when a friend sat and kneeled on the groundsheet of my rather expensive quasar (£350 odd in the 90s) knowing that he was putting damage into the fabric. It leaked ever since that trip.
Blimey. If you can't kneel on a groundsheet without destroying the waterproofing then frankly it's not fit for purpose. I've never been that keen on Terra Nova stuff but frankly I'd expect better of a Quasar. Been kneeling in my Saunders and Hilles for years and the groundsheets are still fine.
Pete.
I've had my TN Solar 2.2 for at least 15 years (Approx use - 300 nights) and it's never occurred to me not to kneel in it, floor is still fine.
As it was in my previous cheap Vango and Coleman tents.
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