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pro/con: 1 long manifold vs. several small manifolds

Okay gents here's the skinny.
Redoing my own personal house system with pex home run to steel panel rads(Myson, Runtal & Pensotti) with TRVs
House is so open plan that it is all just 1 zone, 1 pump, no point in zoning anything.

Since the need is so simple, and I don't need flow setting or zone head control found on the $$$ bought manifolds, I've decided to make my own manifold which I can mostly do with parts I have laying around.

I potentially have 20, yes 20, steel radiators because idiot builder/architect built a stupidly tall 4-story house on a tiny footprint with "spaces" and "areas" but no actual rooms, or doors and big open stairways. In other words a PITA for any heating system.

So I'm thinking 1 BIG long manifold, say a 7 foot long 1-1/4" pipe with 20 1/2" pex ports with shutoffs, with an equal 7 foot return side of the manifold below.

I guess there could be 8 smaller 5 port 3/4" pipe manifolds.

I've not done the actual math, but it would seem that either way the head pressure would be about the same.

Anyone out there in computer land have comments on my "plan"?
...or am I just insane...
Don't answer THAT!


  • This may be a use for parallel reverse return piping, to make sure the flows are equalized to all of your rads, even when some may be controlled (and restricted) by TRV's on each.--NBC
  • ScrewLoose
    ScrewLoose Member Posts: 20
    Parallel reverse is what I've taken out because it didn't work well here. It never worked well, people just lived with as "one of those things". Some of the old rads Never got up to temp, only the rads on the 2nd and 4rth floors heated well.

    I love parallel systems, their cheap, fast and easy. Usually. It's what I usually instal.

    Homerun is new to me, and I have PEX dangling all around this house... probably should've had my manifold setup in mind before running pex... ;)
  • Zman
    Zman Member Posts: 7,330
    I think there is a glitch in the terminology. If you are running all 20 rads back to the boiler,that is a "homerun" system. Reverse return just means you pipe the manifold so the first one in is the last one out.
    It sounds like you could install several remote manifolds around the house and save mechanical room space and a bunch of labor.
    Do you have a drawing?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • icesailor
    icesailor Member Posts: 7,265
    You couldn't possibly have a properly installed parallel reverse return piping system on 4 floors and have some radiators or floors not work. You're dealing with someone else's mistake. I've met "designers" that called themselves "Architects" and they couldn't draw a comic book and have it understandable. The suggestion that you can heat and balance 4 floors on one zone is beyond comprehension and flies in the face of practical physics.

    Your job sounds like good and interesting piping entertainment.

    I'll bet that you can't make an accurate and understandable drawing on how the 4 floors were piped as one zone. If you want to use manifolds, put one on each floor with home runs for that floor. The home runs should be connected as a parallel reverse return. Then, do another parallel reverse return for balance on the manifolds to the 4 floors.
    Bob Bona_4Harvey RamerZman