Hot water heating systems generally operate on a closed loop (i.e. under pressure with the same fluid continually being reheated). This allows water in such systems to oxidize so that it cannot cause ferrous metal system components to corrode, but systems will gradually lose small amounts of fluid. Losses generally occur through evaporation from air vents and valves.
The standard solution to this problem is a make-up water assembly, which automatically feeds small amounts of water to a system in order to offset fluid losses and maintain constant pressure. These assemblies connect to a potable water supply and must include backflow preventers to stop reverse contamination.
Axiom’s Pressure Pal water feeders (available in 6-gallon and 17-gallon sizes) offer two advantages over standard make-up water assemblies. First, they contain a limited amount of fluid. This limits damage in the event of a catastrophic pipe burst, during which a traditional fill assembly would provide fresh water indefinitely. Second, the Pressure Pal can feed a pre-mixed water/glycol solution, which can prevent dilution in systems that contain antifreeze. Additionally, they remove the risk of backflow contamination and can be used to detect leaks in their early stages.