Using pert/pex pipe near the boiler vs copper or black pipe

dronic123

For near boiler piping, if you need 1&1/4 to 2 " pipes with lots of tee's and elbows how does the material COST compare between pert/pex, copper sweat and black pipe overall on average. Assume for black pipe, that we will be trying to use pre-turned nipples wherever available.

Does anyone make a plastic Low Loss Header at a cheaper price than the metal ones?

For doing a complete near boiler piping job, would you recommend pex/pert A or B?

Do you need to support 1&1/4" pex/pert in short lengths of 2? ft?—3ft?—4 ft? in the 1 &1/4 to 2" size?

Is the plastic pipe (in straight lengths?) flexible enough (for the final connection) that you don't need unions as you would with black pipe. And do you just cut it and then replace it whenever you reassemble?

Does copper pipe use unions? Are they useful? or do you just cut and replace?

If you use plastic "B"? pipes, do you need to go a size larger to compensate for the smaller diameter over "nominal" sizing?

pecmsg

Just use Copper for the header.

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1820655#Comment_1820655

Aw…..

In answer to the actual question, there is a minor problem with using PEX or other similar piping for steam heat. The maximum temperature rating of PEX is 200 F. Steam at 0 psig is at 212 F. That really should answer the question.

pecmsg

https://forum.heatinghelp.com/discussion/comment/1820657#Comment_1820657

I miss read

Thought we were talking Hot Water!!!

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1820658#Comment_1820658

Maybe I misread. The OP does say low loss header, which suggests hydronic…

In which case… yeah, you could use PEX. I wouldn't, mind you, as the stuff turns to spaghetti at its rated maximum temperature and would need near continuous support…

dronic123

Yes this is for a hydronic boiler—forgot to mention it —a serious omission I realize, but I'm a rookie.

@Jamie Hall: Does even the 2" Pex turn to soft let alone spaghetti at say 200*?

What about the cost: copper must be substantially more than black pipe but even those 2" black tee's seem expensive?

Is pex and their fittings any cheaper without considering the cost of installation?

Would you be able to use a very short length 2 ft perhaps with fittings instead of a black pipe union? is it flexible enough?

What about Pex "A"—Does it respond to heat the same way as Pex"B"?

PC7060

what 2” black pipe will you need? Typically run copper sized to Boiler BTU size and then use bushing to covert from copper to the legacy 2” pipe. For example, on my boiler, I used 1” copper for 80k boiler connected to existing 2” black pipe.

hot_rod

What temperature will the system run at. I would not use pex on a boiler running 180F.

Also the ID of pex is smaller than copper so be sure to use a pex tube calculator for sizing.

PPI, plastic pipe institute has a free calculator.

8 gpm would be pushing it with 1" pex…

Screenshot 2024-11-16 at 3.14.22 PM.png

JUGHNE

Some PEX type products will never look straight, the curve of the coil is in the memory.

I prefer Black pipe because of the many threaded components (pump flanges, air separator, exp tank, dirt strainer, unions, valves etc…..yes, many of those could be soldered directly to copper but turning pipe nipples is quicker.)

Add up the cost of male adaptors compared to needing none. Most of the near boiler piping is short lengths and most do not have to be a critical length.

I use copper for the connections to the system.

Jamie Hall

PEX A and PEZ B have the same temperature rating. They differ in the way in which they are connected to fittings. Neither one is rated to hold pressure if the water temperature is over 200 F, and both get downright floppy at temperatures even as low as 170 to 180. Even at domestic hot water temperatures, unless they are in a trough or supported every foot or so they sag pretty quickly.

The chief advantage of PEX is the simplicity of joining it. It's not quite idiot proof, but with the correct tools it's pretty darn close. The fittings, at least, up my way are more expensive than copper.

dronic123

thanks all for your comments

@hot_rod : I'm guessing the black pipe is cheaper than copper? and it seemed to me that the pex fittings were expensive but I have no experience to compare

Do you unsweat the copper usually or just cut it?

Is there any trick to using the unions. I thought at the very least, one could use a short length of Pex as the final joint connection instead of a union. Easy to cut and replace. Especially if you buy it straight lengths instead of coil. Pex A type, maybe??. But I will be using a mid efficiency boiler and supply temps of 180—-even 190 possibly.

hot_rod

copper and steel are not so far apart in price now. I would not run pex that hot on a continuous basis

I reuse copper fitting, it takes time to clean them out to reassemble, however

Copper sweat or press would be my choice

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1820685#Comment_1820685

I would say the chief advantage of PEX is how easy it is to run/pull. But yes, the fittings are super easy as well. Even if the fittings are more $$, the cost savings on the actual run distance of the pipe should become dramatically better than copper or steel pretty darn quick. And the fire risk of sweating pipe is not to be ignored. I don't mind if it gets a little pliable. Until someone shows me a picture of pex actually failing in a given application, I will always choose it. And that doesn't include "I heard from a guy about this one time when…"