hj
It is PLUMBING, and why should I take it personally. A boiler lasts 50 years because it operates as a closed system. If you were to use it as a water heater, then the process of always heating fresh water will decrease its potential lifetime. And water heaters or boilers do not explode because the prerssure is building up, since the pressure will remain constant in the absence of a check valve or other backflow preventer. The explosion comes from the rupture of the vessel and the immediate release of the energy contained in the water under normal pressures.
