Here’s a statement that is easy to remember: All boilers that aren’t designed to operate with sustained flue gas condensation should be protected against sustained flue gas condensation.

The latter includes almost all cast-iron sectional boilers, steel boilers and copper tube boilers. These boilers are not intended to operate with sustained flue gas condensation. But, as experienced hydronics trainer Don Pratt, formerly of Mestek Corporation, once told a group of contractors: “Every boiler can be a condensing boiler.” After pausing to enjoy the confused looks from the audience Don clarified his statement: “Given the right operating conditions, every boiler can be a condensing boiler.”