Hydrostatic Head (i.e. HH)

Definition:

HH is a rating of how waterproof a fabric is. (Ranging between roughly 300mm -  10,000mm.) The rating refers to the pressure of water in millimeters i.e. a HH rating of 10,000mm means a column of water could be 10 meters tall before the fabric would start to show water seeping through.

Example: 

1.6 oz HyperD PU4000 has a HH of 4,000 mm. You can find this info in the  specs tab  of the respective fabric. 

Pronunciation: 

/ˌhīdrə-stadik hed /

Glossary Category:

Testing