UKC

Just to clarify, I understand what the hydrostatic head measurement represents, and how it's arrived at in the lab, but I wonder what - if any - difference *in normal use* I might experience between tents with, say, 3000mm and 5000mm HH. I'm trying to decide on my budget for replacing an old faithful tent which is sadly on its last legs!

Thanks in anticipation.

In reply to d80f0u:

I suspect that you will find that design and construction are as important, if not more so, than the materials they use.

In reply to d80f0u:

3000 mm is enough for most applications, but 5000 mm will keep water tight for a longer time, meaning the tent will last longer.

In reply to Sir Stefan:

The durability of tent fabrics is more dependent on things other than hydrostatic head. The use of PU coated polyester vs Silicone coated nylon for instance. Polyester fabrics get weaker with thicker PU coatings, which results in a tradeoff between weight, tear strength (relevant in the light of UV degradation), and durability of the waterproofing. Silicone coated nylon fabrics are lighter and have a higher tensile strength, but are more sensitive to UV-degradation. The latter could be mitigated to some extent by re-applying the silicone coating every now and then (bit of a hassle, but more viable than re-applying a PU coating), although the cost of sil-nylon tents makes them less suited to general car-camping.

Hydrostatic head is most important on groundsheets, as this is the area that deals with most pressure and abrasion. Low hydrostatic heads will result in moist spots under your sleeping mat and other pressure points. 3000mm PU coating is the minimum for wet conditions, and 10.000mm TPU coating is the top-quality stuff.

In reply to timmeehhhh:

Great post. I would add that PU coating unless treated very carefully will peel off (i.e. if you leave it wet for a while, apparently water can weakly dissolve the PU), and even then will still peel off eventually - leaving any discussion about hydrostatic head of the fabric moot.

In reply to timmeehhhh:
Thanks for the OP and timeeehhh's informative reply!

I'm also in the market for a new tent and had got slightly boggled with this hydrostatic head numbers game

Mind you the groundsheet has never been a problem - I use one of those orange survival bags split open and under the tent for stopping abrasion and water. Costs about £5, light and easy to replace if you need to.

In reply to d80f0u:

Thanks all for your helpful responses!