Water and waste water

Le déversoir d’orage is the storm overflow, and the two languages have put two different kinds of weather into the same piece of pipework. French un orage is a thunderstorm and nothing else: it wants lightning and thunder, and a forecast that promises des orages is promising a sky that bangs. The wind-and-rain storm that batters a coast is une tempête, and a gale offshore is un coup de vent. English went the other way with its own word. « Storm » still means violent weather in ordinary speech, but in the drainage trade it has been worn smooth until it means simply rain: « storm water » is whatever runs off a roof, « a storm drain » carries it away on a grey afternoon in March, and a « storm overflow » can spill in a downpour nobody would call a storm. So the French term names the extreme case and the English term names the everyday one. A translator who reaches for « thunderstorm overflow » has written something no engineer says: keep orage for the thunder, and let « storm » stand for the water.