Water Column

The water column is a unit of measurement that indicates the waterproofness of materials. The water column is determined by placing a cylinder filled with water on the material. The more pressure required for the water to penetrate the material, the tighter it is. The water column is given in millimetres. A water column of 3,000 millimetres means that the material can withstand the water pressure that prevails at a depth of three metres. Above this water column, the term "waterproof" is generally used. Not every material is labelled with a water column rating. This includes cotton blended fabric, for example. Of course, this does not mean that this fabric is permeable to water.