Composite buffer tank 

Flexcon’s Argosy buffer/storage tank is a pressurized, rust-proof composite tank designed for use with hot or cold water in hydronic and geothermal systems. Rated to 180°F, its lightweight, injected, High-R closed cell foam insulation is designed to keep temperature losses to less than 1°F per hour. Available in 22-, 40-, 55-, 80- and 120-gallon sizes, units come with four side ports, vent, vacuum breaker and drain.