Direct bury Pex?

[GT26]

Not sure if this is the place to ask?
If I wanted to radiant heat an outdoor garden do I use pex or something else?
I just want to keep from freezing.
Would there be issues with antifreeze migration?
Thanks

 

[Rick Stanley]

Hi GT and Welcome!!

I've been doing some research lately on doing some root zone heating in greenhouses with my Garn. Google "root zone heating".

Good info here: (broken link removed to http://attra.ncat.org/attra-pub/rootzone.html)

Hope this helps,

Rick

 

[Fred61]

Sell your rototiller, chuckle, guffaw, snort!

 

[in hot water]

Not sure if this is the place to ask?
If I wanted to radiant heat an outdoor garden do I use pex or something else?
I just want to keep from freezing.
Would there be issues with antifreeze migration?
Thanks

I would use pex like the Viega FostaPex that has an outer aluminum layer with a protective coat. I had two jobs here in Missouri that used an EPDM tube in gardens, for root zone heating, and some boring insects perforated it! Now they have an expensive soaker hose and no heat in the beds The FostaPex is much easier to lay down and keep in place compared to regular pex.

I also connected a Crop King root zone heating system for a customer. It used a non barrier, double tube EPDM and the wood boiler sure did rust quickly. It was a closed loop pressurized OWF. They installed that system with a crushed gravel over it and developed leaks during the first fill and pressurization, from the sharp base rock he chose.

 

[DaveBP]

I wonder if you couldn't run the PEX through a black poly pipe for protection. Never hear about insects perforating water pipes underground. Filling the poly pipe with water should give good heat conduction from the PEX through the water and through the poly pipe.

Without insulation beneath the heated bed, it might take a lot of heat to get it a little warmer in the root zone.

 

[Como]

Would it be similar to snow melt systems?

 

[in hot water]

They do make a thicker walled poly pipe for underground use. It is used for water service lines and in GEO loop piping. The only issue we ever had with the thick walled water line service tube was the early compression fittings would squirt off! Now they have fittings with gripper teeth, or a barbed inside fitting. Either will work if designed for the application.

The SDR number on the pipe tells the thickness. The number is the OD to wall thickness. SRD 11 would be the OD is 11 times the thickness of the wall. Higher SDR number= thinner wall.

If you want durability use a thicker walled tube, but you do give up some heat transfer. Plastic is an insulator after all. We ran some FEA on pex in radiant and found up to 6 degrees difference from the fluid to outside of the tube. A bit higher temperature difference on the thicker EPDM rubber radiant tube.

I met some greenhouse operators up Wisconsin way that hook onto the pex with a tractor and pull it out of the ground to till the soil, then re-install it.

hr

 

[GT26]

Thanks for the ideas everyone.
I'm wondering if I need all the closely spaced runs if all I'm trying to do is keep it from freezing?
Basically I will have a 10 tree orchard on 2 rows, 10x10 spacing. Will two loops 5' on each side with the returns both coming back up the middle work?
Thanks again.

 

[bigburner]

we have used many thousands of HDPE for GEO with fused coupling with zero issues. Don't know the layout but just well water should do the trick??? Way back when every one had a steam plant of some kind they would in eject stem in to the ground to remove frost, only seen pictures but it was said to still be one of the best ways!!

 

[DaveBP]

GT, what are you trying to grow up there that can't take frozen ground? I'm curious because I've killed a lot of plants up here (SW Maine) trying to grow asian species new to the region.

You couldn't mouse-proof the stems somehow and mulch them well? I've found hardware cloth or vinyl spiral wraps and crushed stone works almost perfectly well. But we don't have pine voles...yet.

 

[GT26]

GT, what are you trying to grow up there that can't take frozen ground? I'm curious because I've killed a lot of plants up here (SW Maine) trying to grow asian species new to the region.

You couldn't mouse-proof the stems somehow and mulch them well? I've found hardware cloth or vinyl spiral wraps and crushed stone works almost perfectly well. But we don't have pine voles...yet.

I have property in northern Idaho that i want to try peachs on.
There are some frost resistant variate's, but there are some late frosts that I think will be a problem.
I also want to try some Hazelnuts, for truffles.

 

[DaveBP]

I found peaches and apricots grew fine here but our southern exposure woke them up too early and we lost the blossoms to late frost. I gave up on them due to the frustration.

Good luck. Try it on a small scale and keep records. I have a lot of weird trees and shrubs growing and blooming that weren't rated for our zone. Sometimes they weren't rated at all because nobody even tried.

 

[btuser]

[quote author="DaveBP" date="1296440020"]I found peaches and apricots grew fine here but our southern exposure woke them up too early and we lost the blossoms to late frost. I gave up on them due to the frustration.

Ain't it the truth. I picked full sun for my apple trees and it may have been a mistake because last December they started to pop after a heavy rain. I don't think the roots are going to be the problem if you pick the right graft. I would think extreeme cold would more damaging to the exposed tree.

How cold does it get in Northern Idaho? I was there once in late August and it was one of the most beautiful places I've ever been. Kinda like New Hampshire only a lot bigger, and you actually have soil.

 

[GT26]

I found peaches and apricots grew fine here but our southern exposure woke them up too early and we lost the blossoms to late frost. I gave up on them due to the frustration.

Ain't it the truth. I picked full sun for my apple trees and it may have been a mistake because last December they started to pop after a heavy rain. I don't think the roots are going to be the problem if you pick the right graft. I would think extreeme cold would more damaging to the exposed tree.

How cold does it get in Northern Idaho? I was there once in late August and it was one of the most beautiful places I've ever been. Kinda like New Hampshire only a lot bigger, and you actually have soil.

According to records 2 in 10 years it can get down to -14 F.
I have only seen 14.
5 in 10 years the frost date is May 16th (32F or less).
I have read of the idea of covering the trees to prevent early growth.
Maybe prune them short and cover with hoop houses?