How tight should an angle stop be?

An angle stop should be tightened securely enough to create a watertight seal but not so tight that it damages the compression fitting or strips the threads. For compression-style angle stops, which are the most common type used in residential plumbing, you typically tighten the nut by hand until it is snug, and then use an adjustable wrench to give it an additional quarter to half turn. Over-tightening can crush the copper supply line or deform the ferrule (the small metal ring), leading to leaks rather than preventing them. If the valve has threaded connections, such as NPT threads into a wall elbow, it should be tightened with pipe tape or dope until it is firmly seated and aligned correctly, usually requiring several turns. The goal is to ensure no water escapes when the main supply is turned on. Always test for leaks after installation by slowly turning on the water and checking the connection points with a dry paper towel to detect even minor moisture. If a leak persists, slightly tightening the nut may help, but if it continues, the fitting may need to be disassembled and reinstalled with a new ferrule.