Choosing the Right Underground Pipe for Your Outdoor Furnace

Choosing the Right Underground Pipe for Your Outdoor Furnace


The output of your system as well as its durability may be negatively affected by the error of installing the wrong kind of insulated pipe for the outdoor boiler. 

PEX, commoPEX tubenly known as cross-linked polyethylene pipe, is a non-corrosive, flexible polymer tubing that is predominantly used for household water supply.

Insulated PEX pipe for wood boilers is often the easiest option for installation, however, it must be done correctly with all factors considered.




 There are lots of options available when it comes to installing the underground outdoor PEX for your outdoor 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. In choosing and purchasing an underground pipe for your system, you need to consider the following features:

  • Flexibility
  • Lower risk of leaks
  • Forever waterproof
  • Low Heat Loss
  • Low-cost great value
If you are using an insulated pipe for an outdoor boiler, the insulation can reduce heat loss and save you up to 4% on your energy bills.
Remember that the hot water from the outdoor wood boiler is routed through the insulated underground PEX pipe to your house or building to be heated. To keep the water hot, your outdoor PEX pipe should be insulated and buried in the ground.
The piping used for supplying heat from a hot water source, such as an outdoor wood furnace, loses heat in 3 ways: Convection, Radiation, and Conduction.


Convection is air moving across a surface similar to a radiator or heat-sync. Radiation is heat moving from hot to cold as 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 metal (electrical wiring).

About Heat Loss/Gain



Think you are smart by saving a buck on an underground insulated PEX pipe? Think again. After 15 years in the industry, we have learned that one of the most important components of an outdoor furnace is the PEX underground pipe. You should NEVER go cheap here. So what else could go wrong?

First, you need to take off the right outer casing. Too thin will fail, and too thick can get brittle and crack. The outer casing needs to be a very specific thickness and elasticity.

Second, some companies charge $12, $14, and even $18 per foot for the underground pipes! They claim it is is not. The experts in this industry all agree that these IMPORTED super high-priced pipes FAIL often, and cost way too much.


Heat Mizer insulated pex pipe uses a strong, flexible corrugated shell or the outer casing which protects the foil wrap and also creates a space of dead air that serves as a conductive break. It is very flexible and can bend up to an 18-inch radius.

  • Forever Waterproof" design
  • Lowest Heat Loss Ever – Less than one degree of heat loss over 200 feet!
  • Industry Leading Warranty - Full Replacement Coverage, including LABOR!
  • Perfect Performance Record - Over 1 Million Sold and ZERO Failures
  • Experts Agree! Our proprietary design has been PERFECTED for over 30 years!
  • Best QUALITY, Best PRICE, Best VALUE!
  • All Insulated PEX customers get FREE Design Service ($695 value)

An independent team did a temperature loss test. The team found out that under a load of 63 500 BTU and 5 GPM, the PEX using a wrap-style radiant barrier insulation only lost 0.87 degree F per 100 ft. The tests were done at a steady state at an average of 3 readings for each test. 

Also, the outer casing must be white. This is our proprietary brand image and it signifies two things:

  • Thickness and elasticity. Remember, too thin will fail, and too thick can get brittle and crack
  • The white outer casing provides a safety feature...if the pipe is damaged in shipping or installation, the white turns to black and you are protected from installing a product that will fail quickly.

Don't do anything until you see this video.

Underground Insulated PEX For Your Outdoor Furnace | Expert Advice on Lowest Heat Loss (Best Value) 


Before Purchasing An Insulated PEX, do not opt for:

  • Black Underground PEX Pipe

Don't EVER use black drain tile. Never! It is not waterproof and will leak! Manufacturers don't care if it leaks because, as drain tile, it doesn't matter. But the underground pipe for an outdoor boiler MUST be waterproof. If it leaks and fills with water, it SUCKS heat out of your system. The earth will absorb an infinite amount of heat. Do NOT use black drain tile. ONLY buy our Heat Miser Pipe with the white outer shell - it is "Forever Waterproof"

  • Foam-filled insulation PEX pipe

Foam-filled underground pipes 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. Don't make the mistake of thinking that spending a much higher price gets you a better product. You can pay $12-$14 per foot (or more) for “Foamy-Filled” pipe imported from Sweden. It is a LOWER grade product with a HIGHER price because of overseas European shipping costs.

What is the Best Way to Insulated PEX Pipe?

One practical way of getting a PEX and insulation is to not buy them separately. You can buy them both together–we can do all the work for you. Our wrap-style radiant barrier insulation uses polyethylene which is a durable closed-cell material with strong impact damping and chemical resistance characteristics. Its physical properties make it well suited to protecting PEX from cold weather while keeping the heat loss to less than a degree.

The radiant barrier insulation has long been used in the heating industry and it obviously is cheaper than other insulations. If you are looking for a PEX pipe that already has radiant barrier pipe insulation, the HEAT MIZER brand is the best insulated pex pipe for sale in the world!

Well done!

We want to congratulate you for being diligent in caring for your outdoor furnace. You can take control of your future by keeping your outdoor boiler healthy, so you can continue saving on your heating bills for decades!

Our goal at is to help you realize the MAX savings and the BEST return on your investment - if you follow our recommendations, you should be able to get 40 years out of your outdoor boiler. You made a big investment in your furnace system so you deserve to realize a great return on that investment. Some customers calculate that they will add more than $250,000 to their retirement, just because of their outdoor furnace!

Therefore, we want you to have special access to the Ultimate Resource On Outdoor Boilers -!

Or you can simply call our office at 231-861-8200 with any questions that you may have.