What is a Hydrostatic Head?

When you are looking through the wide and varied tents which are available to you, and trying to hone in and narrow down your search, you may sometimes come across some terminology more suited to science fiction films! The term ‘Hydrostatic Head’ is the most regular culprit which confuses customers.

Now, the technical explanation for this involves the manufacturer holding a clear tube vertically over the tent material, and each 1000 mm (1 metre) they fill the tube without any water seeping through gains the tent it’s Hydrostatic Head (HH) rating.

This, of course isn’t real life, and many factors, including how heavy the rain is, the duration of rainfall, driving wind, and how sheltered / exposed your position is, will all have a bearing on how long your tent will withstand the rain before drips start to appear.

The recognised industry standard at which a tent is considered waterproof and suitable for summer camping is 1500 HH. Most tents available from World of Camping are at least 3000 HH, some even as much as 6000 HH.

If you cast your mind back around 10 years, then you would find that manufacturers didn’t mention these figures and most tents produced back then would have been in the region of 1000 to 1500 HH and remained, for the most part perfectly waterproof in most conditions. In recent years, competition and a certain amount of one-upmanship has seen the HH of tents rating creeping up and up and no doubt this will continue.

Over time, and exposure to the elements, the waterproofing on all tents will slowly degrade. The most straightforward way to look at the HH rating is that the main difference between a 6000 and a 2000 HH rating is that over the life of the 6000 HH tent, the waterproof coating will take longer to degrade and therefore give you more overall camping time before the tent becomes ineffective against the rain. This amount of time is of course impossible to quantify as too many factors are involved.

Most Manufacturers cannot 100% guarantee that rain will never penetrate their tents.British weather being what it is, we are all very used to prolonged periods of extreme weather, even in the summer, particularly recently! As much as most tents will keep you dry in most conditions, they are not bricks and mortar, and therefore if you are unfortunate enough to experience blizzard conditions whilst camping and the driving rain continues for hours, then small leaks may well occur in your tent, no matter what the HH rating.