Boilers or steam heating devices also have heat exchangers but differ significantly from warm-air heaters. The hydronic system heat exchanger usually consists of finned-pipes or a "water tank." Water is heated inside the heat exchanger and is either pumped or moved by gravity through convection to the radiators. Cracks or holes will usually be evidenced by leaks dripping water onto the burner or refractor. Leaks in heat exchangers almost always means replacement of the boiler. Note: reports of heat exchanger problems should always be substantiated with a second opinion. Contact an qualified air conditioning or heating contractor for service and assistance and for further advice.