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Choosing the Right Underground Insulated Pex Pipe for your Outdoor Wood Furnace

Underground Insulated Pex Pipe
Pre-made, pre-insulated Pex Pipe

We’ll be happy to assist you any
way we can, to make this the
easiest thing you have ever done!

View our updated pex-pipe page at our customer friendly site:

Or be sure to check out the rest of our parts:


If you have any questions please call Randy at 608-519-4664 about our current pex pricing or just look at the new webpage above!

Pre-Insulated Pex Pipe from $6.00 a foot for 3 wrap and $6.80 a foot for 4 wrap!

Our platinum 3 wrap comes wrapped in 21 millimeters of insulation and our platinum 4 wrap comes wrapped in 28 millimeters of insulation.  This is significantly thicker then most manufacturers selling pex pipe.  Also, our platinum pex has lifetime warranty.

Our underground insulated pex tubing features 7mm thick foil wrap over each layer to lock in heat. Our pex does not lose more then one degree over 100 feet with the 3 wrap and half of a degree over 100 feet with the 4 wrap. The standard platinum 3 wrap and 4 wrap come with 2 lines of 1 inch pex tubing. We have the prices listed for those below.


3-wrap pre insulated pex

ALL types of heating supplies are also available, such as all components
for in floor radiant heat systems, baseboard heating, unit heaters,
heat exchangers, plate exchangers, air handlers, pools, hot tubs
and complete installation kits for everything.
Call Randy for pricing at 608-519-4664!


This is the Easiest System for Self Installers!

Simply drop it in the ditch and cover with dirt!

Pre-insulated underground Pex pipe

Pre insulated Pex Pipe for outdoors – underground

What’s nice is that you have 4 Pex lines for heating your domestic hot water tank too.
This also gives you a fill or supply line for your outdoor furnace. The 4 Pex pipes are
surrounded by insulation – FOUR WRAPS of insulation with a black pipe around that.
That is 33% more insulation than triple wrap pipe!
Heat loss is only 1 degree F per 100 foot run!

Choosing the Right Underground Insulated Pex Pipe
for Your Outdoor Wood Furnace

    There are lots of options available when it comes to installing the underground pipe for your outdoor wood furnace. Sectional or seamless, foam or foil wrapped, the right underground piping can make a huge difference in how effective your outdoor wood furnace operates.

It wasn’t too long ago that insulating underground pipe was timely and very expensive. To save on cost most homeowners turned to 10 foot sections of insulated 4 inch PVC pipe that had already been available on the market for other specialty plumbing needs. The outside of each pipe was insulated and wrapped with a plastic bag material. Long pieces of Pex or Pex vs. Pex-Al pipe were fed through these sections of 4 inch pipes. After threading each section the pipes would be glued and sealed using tape. The job was awkward, difficult and labor-intense. Sealing each section proved to be nearly impossible and the pipe would fill with water, causing major heat losses and ruining any advantage of an outdoor wood furnace.

Other sectional pipes have also come onto the market but they all have the same basic flaw, seams underground. The flexible foam variety not only lack adequate insulation value but are susceptible to water penetration through each and every joint underground.

Modern underground pipe lines for outdoor wood furnaces have many advantages; namely, there are no seams buried under the ground. Even within this seamless category there are advantages and disadvantages.

Most manufacturers wisely use Pex pipe in their construction. Foam filled varieties seem to be the best alternative but a deeper investigation proves that foam isn’t always the answer.

The insulation itself should also be considered.  Piping used for supplying heat from a hot water source, such as an outdoor wood furnace, lose heat in 3 ways: Convection, Radiation and Conduction.

is air moving across a surface similar to a radiator or heat-sink. Convection doesn’t apply when outside air is sealed off, such as in insulated Pex pipe.  R-value, a measure of convection, means little when convection is absent.

    Radiation is heat moving from hot to cold, like we all learned about in high school physics.  Conduction, related to convection and radiation has to do with how heat moves through materials like air, foam or plastic.

About Heat Loss/Gain

Click on image for a larger image.

    Radiant heat loss is the most relevant when speaking of underground insulated pipe.  We’ll return to this shortly.

Conduction, heat transferred away by the materials surrounding it, is best controlled by wisely choosing the proper materials for insulation.


Click on image for a larger image.

Foam filled underground pipe use urethane-based foams that limit heat loss based strictly on R-value, trying to limit how much heat is lost to convection.  Foams only limit radiant heat loss by absorbing heat in a slightly limited way and is subject to cracking when rolled up for shipping and then un-rolled at the installation site – because it is so thick and rigid.

The best choice for underground lines is a pipe incorporates foil wrapped insulation.  The foil wrapping retains over 97% of the radiant energy back into the pipe, virtually eliminating heat loss.  Foil wrap must be contained.  Strong, flexible corrugated pipe provides a shell of protection for the foil wrap and also creates a space of dead air that serves as a conductive break.  Having the correct corrugated pipe is important, too stiff and it will crack when bent or compressed, too thin and it may be pierced by rocks or other sharp objects in the ground.  After installation this type of underground pipe, expanding foam should be used on each end to seal the air space, eliminating heat loss by convection. 

Use the blue colored can foam. When everything is installed and in it’s final resting place, tape a cut piece of cardboard securely to both ends of the outer corrugated pipe. Make a hole the size of the
spray nozzle and add foam into each end. Do not add too much. Remember that some expansion will occur. Allow at least 5 hrs. dry time before removing cardboard.

Trench for Pre-Insulated Pex Pipe

Insulated Pex pipe installed and ready to cover up with dirt!

This looks like good dirt here; with no big rocks in it. Avoid dropping rocks on the pipe, so that do not damage it. holes in the outer casing will result in water in the pipe, which dramatically increases heat loss!

outdoor wood furnace concrete pad dimensions

Recommended Dimensions for Concrete Pad

You only need to put the pipe at exact 45 degree angle,
if you are making your own insulated Pex and using PVC pipe –
OR you get cab pre-made insulated Pex from us!