Hydrostatic Head (Tents)

Hydrostatic Head (Tents) – This is the waterproof rating for technical fabrics, measured in millimetres. The higher the rating, the more waterproof the fabric. A rating of 1,500mm is considered waterproof, but for tents it’s best to look for 3,000mm or higher. The measurement is taken by seeing how tall a column of water the fabric can withstand before it begins to let moisture through.

Polycotton tents do not have a Hydrostatic Head rating, as they are not treated in the same way for waterproofing.