"Phil Again" wrote in message

I don't know how common not having a flow valve (check valve?) is. The
system I lived with didn't have them. Yes, it was not a good idea not
having them. I was told expensive (Labor cost mostly) and they fail.
Experts can comment on that statement.

Mine are trouble free for 30 years. Cost? Almost nothing in labor as it is
a simple sweat joint or threaded joint, nothing complex at all.