AQUASKY has invented the leak-safe technology and applied on the stainless connector for the pre-pressurized water storage tank 18 years ago, and they are the standard of the industry for drinking water tank. The polypropylene liner and the butyl diaphragm are made with FDA materials and prevent water from making contact with the metal tank for cleaner, fresher and better tasting water. The butyl rubber is made from a unique ingredient and compound which has the best air resistance comparing with other tank in the market. Brass cap with internal O-ring guarantees no air loss from air-vent. No maintenance is needed during the service life. All RO-PLUS tanks are manufactured at our ISO 9001:2008 registered facilities. NSF listed as the highest standard for RO tank. IAPMO and CE certified for the safest pressure vessel in the market.