Insulated PEX Pipe: Am I Losing Heat Underground?

Insulated PEX Pipe: Am I Losing Heat Underground?


We get calls from customers who worry about snow melting between theirHeat Loss house and outdoor furnace. This can be due to heat loss. If you think that you are losing heat underground we can help you troubleshoot what could be the problem. There are several possible reasons why you are losing heat. 

Here are the possible causes, and the recommended solutions:

1) You may be losing heat underground because you have low-quality pipe. Low-quality components will not provide the PEX insulation value you need to prevent heat loss.

Watch this video and upgrade!

2) You recently installed your PEX pipe underground. This is NOT lost heat from your pex underground, but rather heat escaping from the earth via the path of least resistance - the earth you disturbed while trenching. 

This will go away after the ground settles. You can do the Delta-T Test just to be sure.

3) You are losing heat underground because you have a LEAK in your outer casing. Water fills the outer casing, sucks heat away from your PEX tubing, and that heat gets absorbed by the earth - and the earth can absorb an infinite amount of heat!

Click HERE to watch this video for an explanation.

What Can You Do?

Try This Simple Test...

You can check your PEX underground water line for heat loss in about 5 minutes. This is called a “Delta-T” test  which is simply a measurement of how much heat is lost through your underground pipes into the earth, or the air. 

The instructions for the Delta-T test are as follows:

  • MAKE SURE ALL LOAD IS TURNED OFF.  All unit heaters and furnaces must be disabled, and no hot water faucets can be opened during the test. Make sure nobody is taking a shower, and your outdoor wood furnace blower fan is off, otherwise, the test results are useless.
  • Using a digital contact thermometer, take temp readings at the back of the outdoor furnace on BOTH the Feed Line and Return Line.

Digital Contact Thermometer

  • When taking readings, apply the temp sensor, cover it with insulation, and secure it in place with Velcro or a tie strap. Make sure the sensor is touching a metal surface. Leave attached at least 90 seconds or until temp stops rising on the readout display, whichever is later.
  • For FEED LINE, apply the temp sensor to the fitting or pipe close to the outdoor wood boiler back wall. We want the true outdoor boiler water jacket temp, before any heat loss from the pipe.
  • For RETURN LINE, apply temp sensor to fitting or pipe at least 4 inches from your outdoor wood boiler body. We want the temp coming back from the line before it mixes with the water in the water jacket.
  • Do NOT use an infrared thermometer on PEX or PAP tubing

Infrared Thermometer

It will not give an accurate reading. An Infrared thermometer can only get accurate readings on metal fittings or pipes.

  • Record these readings. If you see temp differences larger than one degree per 100 feet of your PEX underground water line, you are experiencing larger heat loss than is acceptable.

If your heat loss is TOO HIGH , you should consider replacing your PEX pipe underground. Remember that it is critical to select the finest insulated pipe system for your outdoor wood burner in order to limit heat loss and the amount of wood you will consume. Heat Mizer brand insulated PEX underground is proven to save energy and improves the efficiency of your outdoor wood furnace.

Heat Mizer Insulated PEX Pipe

Independent lab studies have shown the heat loss of Heat Mizer insulated PEX to be the lowest in the industry - less than one degree over a 100-foot run! The actual results were about six-tenths of the degree - again, less than one degree. Our customers report that they usually cannot even measure ANY heat loss.

Why is Heat Mizer Brand the BEST Value?

  • "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 2 Million Sold and ZERO Failures
  • Experts Agree! Our proprietary design has been PERFECTED over 30 years!
  • Best QUALITY, Best PRICE, Best VALUE!
  • All Insulated PEX customers get FREE Design Service ($695 value)

Many will try to sell you foam-filled underground pipe for $10, $15, even $18 per foot. This is a waste of money on a poor product that fails. We call it "Do-Over Pipe" because you will have to do it over once it fails underground. I cannot tell you how many people have called us furious that they wasted so much money on a product they thought was supposed to be high quality, but it failed!

So be sure to only use Heat Mizer brand underground insulated PEX from so you can maximize your savings for decades!