Do you -really- think that water coming in at 50 degrees (IINM that is about normal underground temp) at high velocity, at least that of an open fixture, is going to pick up much useable heat in 10 ft?
I suspect he is referring to non-flowing conditions. I kind of lost track here. Does he say that it is in a basement? In my case it is and the pipe is coated with condensate from the point it enters until it disappears into the ceiling joists. Temp in my basement is around 65, too cool to sit down there in a t-shirt.