When we explain a garment in our store, we are asked a recurring question:
"But what is the water column?"
Here is the answer.
Let's see technically the meaning of this measurement system:
THE WATER COLUMN:
It is the value used to indicate the waterproofing of technical garments, from curtains to shells, from sheets to raincoats ...
The water column gives information on the impermeability of a material and indicates the pressure, expressed in millimeters, which can affect a material before it lets water penetrate.
From 1300 mm, the garment is waterproof, while for a value between 400 and 1300 mm the fabric is only water repellent.
Therefore the higher the water column, the greater the impermeability in relation to the time of exposure to water.
But be careful! 
Very high impermeability also lead to ever lower transpiration power. There are garments with 28,000 mm of water column on the market.
Very high impermeability also lead to ever lower transpiration power. There are garments with 28,000 mm of water column on the market. - "Basically you throw yourself into the sea and come out dry !?"
-"Good boy!"
But basically they are a nylon cloth! The water does not pass, of course, but as soon as you move you start sweating like an ox, and in the end you find yourself still soaked.
So high impermeability can be fine in the basin of a tent, in a cloth, in a backpack cover, where the transpiration factor is irrelevant, but in a jacket ... better let it go here, unless you want to undertake a path as a mussel farmer axillary. Rather we prefer a garment with a water column that can protect us from a drizzle, but very breathable. In the event of a flood we wear a poncho, which completely repairs but leaves an adequate air chamber, to facilitate the dispersion of sweat, which, let's not forget, is one of the greatest dangers in winter, together with the wind.
