An air lock is gas trapped in a high point of a liquid-filled pipe system. The gas, being lighter than the liquid, rises to the highest point and restricts the flow of liquid. In very tall systems, the gas can prevent flow entirely.
Flushing the system with high flow or pressures can help move the gas away from the highest point, or a tap can be installed to permit the gas to be vented.
Famous quotes containing the words air and/or lock:
“[Allegory] should ... be very sparingly practised, lest, whilst the writer plays with his own fancies and diverts himself by cutting the air with his wide spread wings, he should soar out of view of his readers, leaving them in confusion and perplexity to explore his viewless track.”
—Sarah Fielding (1710–1768)
“As soon as you are in a social setting, you better take away the key to the lock of your heart and pocket it; those who leave the key in the lock are fools.”
—Johann Wolfgang Von Goethe (1749–1832)