Offsets in pipes between floors?

ChrisJ

I've lived here since 2011 and just realized most of my pipes either have, or are suppose to have an offset in them near the ceiling.  Apparently 2 currently do, one of which is hidden in a cabinet and the other is hidden in a wall.  The third I'm putting back this weekend as it was piped through the closet via copper as mentioned in another thread.

Besides those 3, two other radiators on the second floor which are much larger have a 90 deg elbow coming off of the valve.  I had wondered why those two had that setup and the others didn't and now I know, because their offset is on the first floor.  Ive attached a few photos, one is a drawing of the pipe I'm putting back in, the other is of the offset in a cabinet and the last is of one of 90s on one of the two large radiators  Makes me wonder why the large radiators are piped differently than the smaller ones.  I'd assume the two 45's is superior.



The one I am installing is along side a door, but the door is a recent addition so that isn't the reason for the offset.  These were obviously done to keep the pipe close to the wall but I don't recall seeing this in other houses?  Is this common and I've just been oblivious to it? 



EDIT : The two larger ones have a single 45 coming off of the valve, NOT a 90.  My mistake.

KC_Jones

All mine

Have the double 45 offset at the ceiling.  Mine are all original to the heating system and as far as I can tell it is to keep the pipe as close to the wall as possible.

JStar

Offset

The offsets are there to allow the radiator and pipng to be pitched properly, as well as add swing joints for contraction.

icesailor

Offsets:

A 45 degree offset takes up less room that two 90 degree ells, and has far less resistance.

All fittings have a resistance valve listed as equal to feet of pipe. 90's are far more than a 45 degree ell. 90's add more resistance.

ChrisJ

oops

I just noticed none of mine have 90s.

The two large ones have a single 45 by the radiator.  So why not just do a single 45 on all of them rather than two 45s below the floor?

RobG

Joist?

Could they be offset to go around a joist that spans that side of the house?



Rob

Hap_Hazzard

My guess is

Since the risers to the second floor have to be plumb (or close to it) a 90 will give you a level radiator, so, just as JStar said, you need 2 or more elbows to give you the right pitch. This is not a problem on the first floor because you never have to go level or plumb with the piping.