How much to tighten an angle stop?

When tightening an angle stop, particularly a compression-style valve, it is crucial to avoid over-tightening, which can damage the ferrule or crush the copper pipe. Start by hand-tightening the compression nut until it is snug. Then, use an adjustable wrench to give it an additional quarter to half turn. This is usually sufficient to create a watertight seal. If the valve has threaded connections (NPT), apply pipe tape or thread sealant and tighten until the valve is firmly seated and aligned, typically requiring several turns. After turning the water back on, check for leaks. If a slight leak persists, tighten the nut incrementally, no more than an eighth of a turn at a time, until the leak stops. Over-tightening can strip threads, crack the valve body, or deform the sealing surfaces, leading to more severe leaks. If tightening does not stop the leak, the ferrule may need to be replaced, or the valve may need to be reinstalled. Patience and precision are key to a successful installation.