making my own underground pipe

[northmaine]

Would wrapping my pex with insulation inside a 4" pipe be ok?

 

[leaddog]

It will give some insulation value but you will melt snow. A better way to go is to dig your trench, take some blue board and make a V . Have a contractor come in and spray foam urathane closed cell insulation. You have them make one pass then lay the pipe in and make another pass. Water proof, strong, and cheaper than any other method with more insulation value. I just helped my neighbor and the local spray foam guys did it for $6 a ft. It's so much easier to work with and you won't melt snow. It was in and we were covering it up in less than an hour also.

 

[ken999]

Since the piping will outlive most any stove you hook it to, and its such a mess to install to begin with....why not go with a quality pre-insulated pipe or have your PEX tubing spray foamed in the ditch?

I'm wrapping up the outdoor portion of my install and I went alittle overboard with my piping as I don't want to have to dig it back up ever again. I underdrained my ThermoPEX with 4" pipe and #2 stone wrapped in filter fabric. I then placed the T-PEX on the fabric and backfilled over the pipe with good clean sand, then lined the ditch with 2" rigid foam and backfilled with another foot or so of sand.

I was going to have the T-PEX spray foamed (complete overkill...) but the sprayfoam guy had trouble with his equipment and only got 5-7' done before he broke. That is why I went with the rigid foam. Central Boiler said I didn't need ANY underdrain or additional insulation, but I wanted the peice of mind nowing that I went above and beyond. It's too much work to begin with and I had to big across my blacktop driveway.

I certainly do not want to be re-doing it.

 

[flyingcow]

Would wrapping my pex with insulation inside a 4" pipe be ok?

No. You'll loose a ton of BTU's.
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A version of Thermopex, or as stated closed cell foam it in place. How far of a run are you talking about?

 

[Gooserider]

Also a reminder to double check your heat loads and head loss calculations and make sure you really are putting in a big enough pipe to do the job... Lots of problems from undersized pipe. See other threads on the topic for details.

Gooserider

 

[Robby]

I installed similar to what your talking about, 2 winters, works fine. Used 1 1/4 O2 barrier (pex aluminium pex pipe), wrapped with fiberglass and inserted in 4" sewer pipe (joints glued to prevent seepage of water in). Ran 4 lines and dual electrical lines in case I ever had a problem. Laid the whole works on 4" foam insulation, cut 4.5" slices to fit between lines, laid 4" foam over top. Carefully backfill with shovel until stable, then backfilled with machine. Whole works is 6 feet down. I run water temps of 190F. This Pex pipe is good for 240F. I cannot measure any difference between boiler out temperature and temperature at house. Just shy of 100 ft. distance, 1/2 of which is underground, balance insulated the same way in the basement. I was worried the sewer pipe would get too hot, doesn't seem a problem. There are no joints except ends.


Robby

 

[rowerwet]

so do you melt the snow over your pipe run?

 

[Tony H]

Would wrapping my pex with insulation inside a 4" pipe be ok?

You would lose alot of heat if it's just wrapped with bubble wrap type insulation but I have seen people use the indiviual prewrapped pipe inserted into 4" again this is not the bubble wrap but some hi density foam.
I used a 6" prewrapped foam with 2 1" pex pipes inside buried about 4' down and it works well . In you climate more is better you will not regret insulating it well the first time and try not to have any joints buried in the pex or covering pipe as freeze thaw cycles will cause leaks after a while . The spray foam deal sounds pretty good just make sure the foam used is able to handle direct soil and water contact , I know in my area some folks use the preinsulated sewer pipe and cover with blue foam just like is code for septic lines but you have to make sure you fit the blue foam board well , I would think the spray stuff would be better.