Condensate Return Percentage

Condensate is the best boiler feedwater on the planet: distilled, near zero hardness, near zero dissolved solids, and already sitting at 180–200 °F. Returning 6000 lb/h out of 10,000 lb/h generated is 60% return, and every point you add cuts fuel, makeup water, softener salt, chemical and blowdown together. A closed process plant can hit 90%; a hospital with steam humidifiers and sterilisers may never exceed 40% because much of the steam is consumed rather than condensed.

The number is also a leak detector. Return percentage falling from 75% to 55% over a season almost always means failed steam traps blowing live steam to the vent, or a buried return line leaking into the ground, and the makeup meter will confirm it. The caution on the treatment side is that returned condensate is not automatically good condensate: it picks up carbonic acid from CO₂ released by feedwater alkalinity, and that acid eats grooves along the bottom of return lines. If your return conductivity or iron suddenly spikes, dump the condensate to drain until you find the process leak or the corrosion source, rather than feeding it to the boiler.