As funny as it is for us to drag members of staff out to the yard so we can soak them "for quality control purposes" there's much more that goes in to making sure every garment we produce here at EQUIDRY really is as waterproof as we say.

Hydrostatic head, or HH, is a unit of measurement given to fabrics after a laboratory tests them to indicate how waterproof they are. The measurement is provided in millimetres (mm) and is calculated by carrying out a test that involves using a tube that’s open at each end. The fabric is tightly secured over one end of the tube and at the other, the tube is gradually filled with pressurised water. When the water starts to come through the fabric, the height of the water is measured and that is the hydrostatic head rating of the fabric that is then used to produce your EQUIDRY. 

So, in short, if water starts to seep through when the water is at 3 metres / 3000mm, the hydrostatic head rating for that fabric is HH 3000mm. Over time machines have been improved so that they no longer need to use such huge long tubes and they can now use a much smaller machine to simulate that amount of water which is why at EQUIDRY we can test our fabrics to ensure they are always a HH rating of 15,000 - 20,000mm.