Hello all,

I have a two story, two family house that is on 1 heating loop, 1 zone, for hot water radiators up & down. The current configuration is a 1.25" threaded pipe loop and is operated by a taco 007. Small sections of the loop which have failed were repaired by the previous owner with 1" copper (not sure if this matters). The radiators tee off and back to the main loop with 1/2" pipe.

The first floor is basically 2x4 sleepers on slab with a subfloor and hardwood. The heating loop runs around the perimeter of the house (160') and lays on the slab inbetween the 2x4 sleepers.

Ok, now that I got the lengthy (sorry) background information out here is my question. Because of hurricane sandy the floors are ripped out and I'd like to add a second heating loop / zone for the first floor. My plan was to leave the upstairs radiators on the existing loop and plug the T fittings that were hooked up to the first floor radiators. Run a new pex loop for the first floor radiators and replace the old weil mclain gas boiler with two high efficient somethings.

How do I determine what size the new pex loop should be for the first floor? I was guessing 1" should be more than adequate? Also anyone see any problems with this other than obviously disonnecting the first floor radiators from the existing loop without breaking 60 year old piping.

I appreciate any advice here.