I have hot water heat with cast iron radiators. Right now the piping
is 3/4 in. copper in the immediate vicinity of the boiler (which is
about 15 years old) but it then connects to old steel pipes. The steel
pipes are sizable (the mains are maybe 2.5 in. and the loops to each
radiator are 1.5 in.). I think the system used to be gravity-driven
judging by the size of the pipes and the way the mains slope slightly
up away from the boiler. But now there is a pump. I have been
thinking I might want to replace the old steel piping, mainly to
increase headroom in the basement, but also to reroute some of the
lines which go through outside walls. Could I replace the steel with
copper, and if so, how to size the lines? Is there any kind of plastic
piping that is suitable for this application? Are there particular
advantages or disadvantages of doing this I should know about? Thanks,
-- H