# Pex Al Pex as underground line??



## 4hiswork (Sep 27, 2010)

Barn is now built, called econoburn and asked what size line I should use??  They said 1" is all I need based on the fact that my unit will only produce 100,000 btu's.  I bought some Vanguard PEX at Lowe's but I am rethinking that decision...I don't like how much it "grows" when heated and I am thinking that I need the O2 barrier.  Has anyone used the Pex Al Pex for underground?  I am planning on spray foaming the lines to the house (about 70 feet) and then to the pool (about 35 feet)


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## juddspaintballs (Sep 27, 2010)

Do you need the O2 barrier if the PEX is spray foamed in place?  In theory, O2 shouldn't get through the foam, should it?


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## shawntitan (Sep 27, 2010)

I used pex al pex underground,  then spray foamed. No problems.


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## jj2003 (Sep 27, 2010)

i was thinking on doing the same thing. what is pex al pex? and the 1 '' pex you got from lowes is the red or the white ?


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## Tennman (Sep 27, 2010)

As I understand it from reading on the Upon Wirsbo products, the aluminum covering was the first generation method of producing an oxygen barrier. The latest technology is done chemically by something on the outside. Pex-al-pex may be fine but in my experience with multilayer products over time are problematic. I don't have any data to confirm, but I just never wanted to see this line ever again and went with the lowest risk, not lowest price approach. And Closed cell foam is impervious to water molecules I doubt even sprayed on the pex would keep oxygen molecules out. I certainly expect over time there to be a very small gap between my foam and the pex. Besides there will be lots of surface in your installation exposed to the air. I've never seen anything truly bond to polyethylene. I certainly didn't expect the polyurethane foam to stay truly bonded long term. I was able to easily peel the polyurethane foam from my first attempt insulating off the pex.


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## killick (Sep 27, 2010)

JT, I have Kaitec Pex-Al-PEX lines underground from the boiler shed to the house. They have been in for 10 years with no problems and were run inside a 4" PVC conduit and insulated on top. The Kaitec has started to fail, which apparently is not uncommon, and will be replaced with Heat Pex when my Econoburn boiler is installed in the next week or so. Facing the replacement of the Kaitec I am thankful I originally decided to run the lines in the 4" PVC as we should be able to pull the old out and feed the new Pex tubing through. I would strongly recommend this procedure especially if your lines have to run under driveways or such. Mine run under the shed slab, a retaining wall and garden and have the electrical line installed above it in the trench. A major pia to have to dig and replace. I have the Econoburn 150 and ran 1 1/4" lines about 70' to the house. 

Earl


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## heaterman (Sep 27, 2010)

My experience has been that when regular pex is "confined" IE: underground or in cement, it grows radially rather than longitudinally. The only time I have seen problems with it moving into the basement is when it has been installed in a sleeve such as another poster detailed above. 

Ki-Tec has shown a propensity to delaminate over time and I would not recommend its use. Other PAP products like Viega Fost-Pex in particular have worked very well for me. I would recommend it without hesitation. Ki-Tec was was another type of product altogether requiring special fittings and such. 

As far as the O2 barrier goes, yes by all means return the tube you have if it is regular plumbing pex for hot and cold water. Even in semi open systems it is worth it to keep as much O2 out as possible. It helps your water treatment chemicals to last longer at the very least. O2 molecules are smaller than H2O molecules and as such can pass right through the walls of non-barrier tube. Do the boy scout thing and take every precaution.


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## 4hiswork (Sep 28, 2010)

joe2003 said:
			
		

> i was thinking on doing the same thing. what is pex al pex? and the 1 '' pex you got from lowes is the red or the white ?


t
The tube from lowe's was white and Vanguard brand...the pex al pex is a sandwich of pex with aluminum in the middle.  This type of pex does not suffer from expansion and will stay where it is put.  But as others have posted this may not be the best choice!


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## 4hiswork (Sep 28, 2010)

heaterman said:
			
		

> My experience has been that when regular pex is "confined" IE: underground or in cement, it grows radially rather than longitudinally. The only time I have seen problems with it moving into the basement is when it has been installed in a sleeve such as another poster detailed above.
> 
> Ki-Tec has shown a propensity to delaminate over time and I would not recommend its use. Other PAP products like Viega Fost-Pex in particular have worked very well for me. I would recommend it without hesitation. Ki-Tec was was another type of product altogether requiring special fittings and such.
> 
> As far as the O2 barrier goes, yes by all means return the tube you have if it is regular plumbing pex for hot and cold water. Even in semi open systems it is worth it to keep as much O2 out as possible. It helps your water treatment chemicals to last longer at the very least. O2 molecules are smaller than H2O molecules and as such can pass right through the walls of non-barrier tube. Do the boy scout thing and take every precaution.



I really wanted to thank you and really everyone that has commented here on this...underground lines are HUGE!!  This is something I have got to get right!  Thanks again to everyone.


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## Tony H (Sep 29, 2010)

I have pex-al installed indoors and it is much stiffer less bendable pipe that regular O2 barrier pipe and it expands and moves less. For outdoors I don't know if there is any reason use it FYI it is MORE expensive than std O2 barrier pipe and would not be the low $$ approach. I used Logstor outdoor pipe and would probably use the same or similar product plus I would spray closed cell foam over it . The downside is most of this pipe is pretty large and would not be easy to pull thru another pipe. We even tested it with a buddy who does underground pipe and other than a really short straight run the sheath on most of these type pipes will shred under the stress of the pull.


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## mwk1000 (Sep 30, 2010)

Pex -al-pex also has much better flow characteristics that regular pex. 1" pex-al-pex and 1" pex are NOT the same , pex-al-pex is stiffer / larger ID and better = lower head

C values are multipliers for flow resistance compare 1" pex and 1" pex-al-pex
3/8" PEX (I.D. =0.36") 2.9336
1/2" PEX (I.D. = 0.475") 0.7862
5/8" PEX (I.D. = 0.584") 0.2947
3/4" PEX (I.D. = 0.670") 0.1535
1" PEX (I.D. = 0.86") 0.04688

3/8" PEX-AL-PEX (I.D. = 0.35") 3.354
1/2" PEX-AL-PEX (I.D. = 0.47") 0.8267
5/8" PEX-AL-PEX (I.D. = 0.63") 0.2056
3/4" PEX-AL-PEX (I.D. = 0.79") 0.07016
1" PEX-AL-PEX (I.D. = 0.98") 0.0252


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