pipe size reduction - will it affect radiator heat

redcar383

My basement has cast iron hot water heating pipes. In order to remodel my basement these will have to be moved much closer to the walls. Question - I have a number of feeds of 3/4" off of the 1" main runs. In using Pex rated heat pipe and fittings I have to go to 1/2 heat pipe pex for the threads to match up. Will this affect the radiant heat output of the radiators?

Thank you

EYoder

Are these cast iron radiators or baseboard? 1/2" pex can handle a good size cast rad if each is piped individually.

SuperJ

If you pipe your rads in parallel you'll likely be fine with 1/2" pex. But if you can post some more specifics about your system you'll get better feedback, like rad size/output, pipe runs, water temp, etc.
Pictures are good too.

Ironman

The piping in your system was carefully balanced when it was installed - particularly if it was originally gravity flow. If you change part of it, that will throw it out of balance.

Water takes the path of least resistance. While 1/2" may carry enough flow if the entire system was designed for it, it will most certainly be too small if the other rad's have larger piping.

What I'm saying is that the system must be viewed as a whole in designing and selecting pipe sizes. You can't just redo the pipe size of only part of it. That's why more info is needed.

redcar383

Thank you! Bob, Superj and Eyoder.. I (may) have enough information at this point..
with sincerely very much thanks Gentlemen

Tinman

Run a 1/2" Pex-Al-Pex supply and return from each radiator back to the boiler room and connect them to manifolds with flow meters and balancing valves. I.e. Homerun manifold distribution system.