Accessories for Ultra Clear ® RO 80 l tank. The filter housing is made of natural PP. For adsorption of CO2, lime hydrate with color indicator is used. When the filter is exhausted, it will get a bluish color. The Vent filter 2'', built on storage tanks, is used to clean the inlet air. A check valve, mounted in the overflow pipe assures filtered ventilation. Accessories for Ultra Clear ® RO 80 l tank. The filter housing is made of natural PP. For adsorption of CO2, lime hydrate with color indicator is used. When the filter is exhausted, it will get a bluish color. The Vent filter 2'', built on storage tanks, is used to clean the inlet air. A check valve, mounted in the overflow pipe assures filtered ventilation.