Crystallized Waterproofing Mortar (2K) It produces insoluble crystals by reacting with the chemicals in the structure of the concrete, thus providing water isolation from both the negative and positive sides. It has been used successfully for years in the internal insulation of basements and water tank-swimming pool insulation. It is hygienic, suitable for use in drinking water tanks and water tightness (negative and positive side) up to 13.8 bar water pressure has been documented. It has CE certificate in EN 1504-2 standard.