There should also be a rubber washer between faucet and sink top also to prevent water
ingress. One problem I have found from replacing several on our cat is that the threaded rod and C washer is often plated steel
and will rust and fall apart. I replace the threaded rod with a stainless one and have made replica C washers from stainless (very hard work) and Tufnol (which is much easier). We use pull out shower
fittings and changing the shower
hose with the standard flexible connector is almost impossible in situ. The pull out shower flexible connector is too short and of poor quality, fails quickly due to constant flexing and is non standard so you cannot buy them, so have cannabolised the old end fittings and soldered them on to a longer piece of copper tube so that I can now replace the shower hose fairly easily when it fails.