This is a fast setting material based on a potable water approved natural cement, it is an environmentally friendly, fast setting, water stopping material that at 20ºc starts to set in 90 seconds and is totally set in 2½ minutes.It is also Reg.31 approved for contact with drinking water. WATERSTOP only requires to be added to water and mixed for two minutes (see mixing instructions for further details) and provides a waterproof barrier. It can be used in cold & wet conditions, sets under water and from a minimum of 1 mm can be, if required, built up layer on layer to any thickness.