Priming, that's why he opened the cylinder drains - to vent the carried over water, although most of it still goes up the chimney. Usually caused by the boiler being too full, or the water inside being dirty.
That's what you call a priming traction engine he's left the pump or injector on he's had to open the cylinder drain cocks to get the water level back down the gauge glass that's what he's looking at it'll be fine no dramas 👍
er, you really don't know what you are talking about. You have heard various phrases but just to use them in a sentence does not make you an expert. Engine caught the water. That is all. Slide valve lifts off seat so likely no damage. Best to stay silent and let others only think you might not know than to put it in print and confirm it for them.
