The hydrostatic Head! What is it?

The waterproof rating of the tent is a crucial factor in deciding which tent to purchase. Hydrostatic Head (HH) is a measure of the waterproof qualities of tent fabric and this information should be provided in the tent's marketing information.

The tent fabric is tested to determine its ability to withstand the pressure generated by a column of water without leaking. For European camping use it is advisable to purchase a tent with a HH or PU rating of at least 3000. Some cheaper tents will have a lower HH rating such as 1000 or 1500 and will consequently be less waterproof and may leak.

This level of waterproofing shouldn't deteriorate too much during use except where the tent fabric is "bent double", ie it is folded over to such an extent that it causes a crease. The HH rating along this crease line will reduce as a consequence and will thus create a less waterproof tent. To avoid this problem the tent should be packed in such a way as to avoid creases and shouldn't be "squashed up" in the storage bag. Puchasing a tent with an oversized bag helps to avoid this problem.

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