With the advent of pex becoming more prominent in plumbing repairs, retrofitting and new installations, its it’s ease of use that makes it attractive. If you come upon pex, look at brass fittings for suspect conditions.
One shortcoming is zinc within the brass.
Others are crimp and attachment placement dezincification.
Zinc is a ***highly reactive meta***l and it has a weak ability to bond to other metals at the atomic level. When water flows through the fittings and valves it corrodes the metal; zinc leaches from brass and creates a powdery buildup inside the fittings. This corrosion process is known as dezincification, and it causes two main problems. First, the zinc builds up inside the walls of the fitting which decreases water flow and eventually causes a blockage. Second, the porous copper-rich structure that is left behind has little mechanical strength and is prone to seepage and structural failure.
Look for whitish powdery surfaces on brass fittings.