OK. So, twice the pipe that would otherwise (e.g., series connected radiators) be needed. Besides the obvious capability of "local control" at each radiator, you also don't have the problem of the "room at the end of the line" getting the least heat! :<
But wouldn't that be "buried" (in a wall, below a floor, etc.)?
Note that "not bad" is not the same as "good"! ;-)
Our gas feed was just replaced (I guess they do it periodically as I have seen trucks methodically digging up people's yards all around town). The feed *at* the meter is metallic. But, below grade, some kind of plastic/nylon.
Amusing to watch them "pull" this new gasline *through* the old one. Have a gizmo that looks like a conical knife. Attached to a 3/8" (?) diameter steel cable. New gas line follows the broad end of the cone.
Cable is threaded through the existing gas line (from either the street end or the meter end, depends on logistics). Then, the free end is attached to the bucket on a back hoe. Back hoe operator repeatedly lifts and lowers the bucket (taking up the slack each time) to *pull* the assembly through the old gas line. Knife edges on the exterior of the cone slice the old gas line to shreds as it makes way for the new gas line to follow it. Incredible labor saver. However, if old gas line is pinched anywhere (e.g., tree root growing around it) I guess the forces exerted can snap the cable (connection to the "mule")
Always interesting to see how people solve problems.
I use 1" galvanize outside for feed lines to irrigation. Once below grade, I transition to PVC (we have essentially two grades of PVC here: thin wall and thick wall). Indoors, potable water is all copper.