Pex vs Steel pipe

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joecool85

Minister of Fire
I'm going to be building my boiler shed 15' from the house and I'm curious about running 1.25" steel pipe in a 4-6" PVC pipe 3' under the ground. Any reason this would be better or worse than pex? I'm thinking it might be cheaper, but need to price out steel pipe.
 
beauty about steal pipe is if it ever freezes on you you can hook a welder up to it one clamp on either end and heat it up to unthaw it , cant do that with pex
 
webie said:
beauty about steal pipe is if it ever freezes on you you can hook a welder up to it one clamp on either end and heat it uo to un thaw it , cant do that with pex

That's a neat trick. Looks like price wise it'll be about the same. I can get 40' of 1.25" black pipe for $80 out the door at home depot, put it in 20' of 4" PVC ($16) and wrap the steel pipes with some insulation ($?) and I should be good to go. I'm going to install the PVC at a 2-3 degree downhill slope into the basement so that if any moisture gets in somehow, it'll drip into my basement instead of water logging my insulation. Probably not possible with longer distance, but since it'll be about 15', shouldn't be an issue.
 
joecool85 said:
wrap the steel pipes with some insulation

For such a short distance, I'd fill the the space between the steel pipes and the PVC with closed cell spray in foam. It would be an easy fill and you'd get high R value and save any issues with water getting in.
 
juddspaintballs said:
joecool85 said:
wrap the steel pipes with some insulation

For such a short distance, I'd fill the the space between the steel pipes and the PVC with closed cell spray in foam. It would be an easy fill and you'd get high R value and save any issues with water getting in.


Judd, just curious, but how would you get the spray foam into the PVC pipe?
 
If it's only 15' long, it wouldn't be all that difficult to apply with a longer applicator nozzle. You only have to reach in 7.5' max. Heck, you could mix together pourable expanding foam and pour it in from one end if you had the pipe standing on end prior to installation.
 
juddspaintballs said:
If it's only 15' long, it wouldn't be all that difficult to apply with a longer applicator nozzle. You only have to reach in 7.5' max. Heck, you could mix together pourable expanding foam and pour it in from one end if you had the pipe standing on end prior to installation.

Couldn't you also just drill fill holes every foot or so, that way you could probably be sure the pipe cavity was completely filled?
 
patch53 said:
Couldn't you also just drill fill holes every foot or so, that way you could probably be sure the pipe cavity was completely filled?

Yes, but if you wanted to keep the waterproof integrity of the pipe then you'd have to reseal the holes. I know it's closed cell foam...but if you're going to the extent of using PVC vs. drain pipe...
 
If your only going 15 feet go with the pex, install spacers ( 2" insulation board) between the lines , tape them together and spray about six inches of closed cell all the way around it. No PVC needed. Should be around $300.00 for the foam.
 
Just my 2cents, but for a short run like that I'd oversize and go with PEX so I never had to give a thought about rusty pipes underground for the rest of my life. Two years ago had to find a leaking underground rusted pipe to an outside faucet. So with today's materials I'll never have steel pipe underground.
 
for about $320 you can run logstar or thermopex 1-1/4" and not have so much work but If you need the larger I.D. run the steel.
 
webie said:
beauty about steal pipe is if it ever freezes on you you can hook a welder up to it one clamp on either end and heat it up to unthaw it , cant do that with pex
Be carefull what welder you use for this. I worked at a rental house & a very expensive gas driven tow behind welder came back with the armature windings hanging out the cooling slots. It was used for pipe thawing. The owner wasn't too happy, Randy
 
Tennman said:
Just my 2cents, but for a short run like that I'd oversize and go with PEX so I never had to give a thought about rusty pipes underground for the rest of my life. Two years ago had to find a leaking underground rusted pipe to an outside faucet. So with today's materials I'll never have steel pipe underground.

I'm not concerned about rust. The pipes will be in a PVC pipe, at a downhill slope...water can't get in, and if it does somehow, it can't stay in. I'd be more concerned about plastic degradation in the case of over heating the boiler if I used pex.

I think I may oversize to 1.5" since the price difference in steel pipe is negligible.
 
If price were not a concern for me (and it is because I'm going almost 100'), I would use steel pipe sealed in foam filled PVC as well. I'm leaning toward going with PEX inside foam filled drain pipe though.
 
juddspaintballs said:
If price were not a concern for me (and it is because I'm going almost 100'), I would use steel pipe sealed in foam filled PVC as well. I'm leaning toward going with PEX inside foam filled drain pipe though.

Steel in PVC is cheaper than insulated pex. $18 for 10' of 1.25" steel pipe x 2 = $36 + $8 per 10' of 4" PVC = $44. So $4.40 per foot plus insulation. Not bad on price. Probably more of a pain to lay than pex though, especially for 100' lol.
 
Yeah, installation would be a real PITA for that distance. Gluing the PVC together so it doesn't break over the course of a 100' trench that isn't 100% level could be tough.
 
joecool85 said:
I'd be more concerned about plastic degradation in the case of over heating the boiler if I used pex.

This is a valid thought but Pex will tolerate to a point overheating. I ran mine up to 235 degrees (not one of my brightest moves) once over this winter and I didn't have a problem. I'd look at pex more in the case if you every froze it as I think it will be more tolerant to freezing over steel.
 
when and if I get my boiler I think I will try the steel centered in pvc with urethane foam. I plan on building a shed and or shed/poolhouse to house the boiler about 15' feet from the house. Why do so many go 100's of feet away? It just seems expensive and a lot of work. About 2-1/2 years ago I built an attached garage with the intention of siting the boiler in there. I put 28' feet of 1" dual logstor pipe underneath the slab and into the basement only to later find out boiler in garage is a no go (codes). My dad had a wood stove in the garage for 30 years and he was an insurance salesman. So I never even gave it a thought . Oops! when someone earlier suggested using the logstor/thermopex style pipe I decided to check out thickness of the insulation on mine. It turns out the the pex at it's thinnest is only insulated with about 5/8'' of foam and the 2 lines are separated by 3/8". Total pipe diameter is just over 4 inches. I think I'm going to go with two six in pvc pipes with either 1-1/4 or 1-1/2 steel with pourable foam. I can get 8 cubic feet of 2lb marine polyurethane foam for 62 dollars + S&H.
 
white pine said:
when and if I get my boiler I think I will try the steel centered in pvc with urethane foam. I plan on building a shed and or shed/poolhouse to house the boiler about 15' feet from the house. Why do so many go 100's of feet away? It just seems expensive and a lot of work. About 2-1/2 years ago I built an attached garage with the intention of siting the boiler in there. I put 28' feet of 1" dual logstor pipe underneath the slab and into the basement only to later find out boiler in garage is a no go (codes). My dad had a wood stove in the garage for 30 years and he was an insurance salesman. So I never even gave it a thought . Oops! when someone earlier suggested using the logstor/thermopex style pipe I decided to check out thickness of the insulation on mine. It turns out the the pex at it's thinnest is only insulated with about 5/8'' of foam and the 2 lines are separated by 3/8". Total pipe diameter is just over 4 inches. I think I'm going to go with two six in pvc pipes with either 1-1/4 or 1-1/2 steel with pourable foam. I can get 8 cubic feet of 2lb marine polyurethane foam for 62 dollars + S&H.

You might still be able to put the boiler in the garage if you wall it off to make it into a boiler room. With only 28ft of run your lines should be ok as you would loose very little in a short run. I think if you make a fire wall with out a door going into the garage it will pass code. But check first.
leaddog
 
There is a max temp rating for pex, but for the normal usage range it depends on pressure. Typical boiler pressure is 12-20psi, at which case I'd be willing to bet pex could hold up very well, especially the higher quality ones (pex-a). The only reason I'd consider steel instead of pex would be the ease of joining and not needing to own/rent a set of crimpers/expander tool. If those are hard to get then I'd definately go with steel. the price of 1 1/2 fittings aren't cheap.

Steel underground between two buildings is also a conductor, so I would suggest a grounding scheme to prevent electrocution in case one end became energized.
 
btuser said:
There is a max temp rating for pex, but for the normal usage range it depends on pressure. Typical boiler pressure is 12-20psi, at which case I'd be willing to bet pex could hold up very well, especially the higher quality ones (pex-a). The only reason I'd consider steel instead of pex would be the ease of joining and not needing to own/rent a set of crimpers/expander tool. If those are hard to get then I'd definately go with steel. the price of 1 1/2 fittings aren't cheap.

Steel underground between two buildings is also a conductor, so I would suggest a grounding scheme to prevent electrocution in case one end became energized.

Good point about a grounding scheme. Not an issue if the steel was in the ground, but since it won't be (inside PVC which is an insulator), grounding might be a wise idea. Although, wouldn't it be grounded via the auto fill pipe?
 
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