Relocating Feed / Return Radiator Lines

Help Support Plumbing Forums:

europe72dead

Active Member
Joined
Apr 7, 2020
Messages
29
Reaction score
2
Location
New Jersey
I’m relocating two 3/4” steel radiator lines that come up from my basement, through my kitchen into my master bathroom on the second floor.

I’m planning to take the route outlined in blue and in doing so I’ll be adding roughly 22 additional feet of line and 4 additional elbows per run.

Questions-

1) Will this additional linear footage be problematic at all? I’d rather take the interior wall route than have the pipes run up the exterior wall

2) I’m planning to run Pex al pex since this is a two pipe closed system (converted gravity system) - what size is best to replace 3/4” steel pipe, 3/4” or 1” Pex? I will be replacing the cast iron radiator with a Runtal steel baseboard or something comparable.

3) Any concerns with water temperature and Pex al pex ? When heating up my boiler was reading around 170 degrees however 20 minutes later its now off and dropped to 145. I know Pex shouldn’t go above 180 or 200 degrees. I’m honestly not sure how high my boiler goes on a regular basis. I have a Utica MGB170

Thanks for the help!

A1E5BC67-D059-46DA-88CB-4E90EF5AEF58.jpeg
 
Last edited:

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
243
Reaction score
61
Location
Iowa
Your piping max length is a function of the longest run of piping. If your new run becomes the longest run then it'll effect your pumping ability. If you have a longer run somewhere else your fine.

You should replace 3/4 steel with 1",but without a lot of very specific info I don't know if you can get away with 3/4.

Set your high limit to 180 and you should be fine with the pex temp. Just leave room for expansion of the pex. It'll move a lot.
 

europe72dead

Active Member
Joined
Apr 7, 2020
Messages
29
Reaction score
2
Location
New Jersey
This could very likely be the longest run in the system but I’m not 100% certain. If I had to guess- it will be.

If it’s safer to run 1” Pex al Pex in place of my existing 3/4” galvanized I will do that. I will then have to reduce down to 1/2” when connecting into the new baseboard heater.

I’m not concerned with the cost difference of 3/4” or 1” Pex, I just want the correct application for what I’m trying to accomplish.
 

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
243
Reaction score
61
Location
Iowa
If your going to be the longest run you may need a different pump, depends on how close to the borderline your current pump is. Not a huge deal, just know it's a possibility.
 

europe72dead

Active Member
Joined
Apr 7, 2020
Messages
29
Reaction score
2
Location
New Jersey
Thank you. What is the downside to replacing my existing 3/4” run with 3/4” Pex al Pex?

Lastly is there any potential negatives from running the 1” Pex al Pex?
 

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
243
Reaction score
61
Location
Iowa
Gpm. You'll get different temps at different gpms at different points in the system. Your making the I.D. Smaller with pex. There are a lot of specifics that'll let you know what size you need. No real downside to going 1" in pex. It's not actually very much larger than your current metal piping. But 3/4 could be constricting, enough to restrict your btu's enough, to not give enough heat when it gets really cold. Or not. Your pump is the limiting factor, but oversizing the pump makes noise. Being a free advise site I'm not obliged to figure your entire system for you. Which is what it'd take to tell you exactly.
 

europe72dead

Active Member
Joined
Apr 7, 2020
Messages
29
Reaction score
2
Location
New Jersey
Will certainly go with 1” Pex al Pex. Your help has been much appreciated.

My last question, do you see any issues with the elbows I’d be using? I’ll try to bend my turns to create a long sweep but may still need to incorporate elbows.

Thanks again
 

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
243
Reaction score
61
Location
Iowa
That's is actually a downside with larger pex, it's harder to work with. The 90's can create an issue especially if your making a new "longest run". But once again. The pump will be the determining factor on that one.
 

europe72dead

Active Member
Joined
Apr 7, 2020
Messages
29
Reaction score
2
Location
New Jersey
One additional thought to rerouting these supply return lines.

Instead of adding the 22+ feet to each run, I can also run the Pex through my exterior wall where the existing 4” waste pipe is. I will likely use a 3”pvc waste pipe and have room on both sides to run Pex. Using this route only adds roughly 6 feet per run instead of 22 feet.

I assume I can certainly get away with the 3/4” Pex using this route.

I can likely insulate with 2” foam board which is R10
 

europe72dead

Active Member
Joined
Apr 7, 2020
Messages
29
Reaction score
2
Location
New Jersey
Not at all unfortunately. I just know there is currently 3/4” pipe and I’d only be adding 6’ to the run. It may even be more like 4-5’ additional length as I’ll be able to remove some bends going to the current radiator on the second floor.
 

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
243
Reaction score
61
Location
Iowa
Since you don't knots specific I'd recommend using 1".

3/4 will move a lot of btu's but I'm not inclined to reverse engineer you while system for you.
 

europe72dead

Active Member
Joined
Apr 7, 2020
Messages
29
Reaction score
2
Location
New Jersey
Will move forward replacing with 1” and go through the exterior wall which only adds a yard or two of addition line per pipe. This seems much better than adding over 20 feet to each run.

My only concern is with minimal insulation inside the exterior wall that the new pipes will go through however it seems like my only option at this point.....
 
Top