Hydronic expansion tanks are the latest in a long line of quality products brought to you by Flexcon Industries. Constructed of deep drawn welded steel domes, HTX tanks feature butyl diaphragms engineered for longer life. Butyl rubber is the material of choice for American heating systems as it offers low permeability rates at higher temperatures. Their oversized diaphragm maximizes tank drawdown, and minimizes wear. This design virtually eliminates diaphragm stretch, which enhances longevity. These tanks are not to be used in open or potable (domestic water systems).