Use PEX-Flex Pipe to Save Money

Insulated PEX-Flex piping moves water from wood furnaces or solar heaters with little heat loss, improving system efficiency.
By Steve Maxwell
August/September 2012
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Steve Maxwell installs PEX-Flex pipe. This insulated piping product can be a good choice for a wood-burning or solar water-heating system.

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If you’re considering installing underground hot water pipes on your homestead, take a look at an insulated piping product called PEX-Flex. I use an outdoor wood furnace to heat my domestic water and have found this piping product to be an energy-efficient choice for moving hot water. It would also be a good choice for connecting to solar water heaters.

PEX-Flex is made of a pair of PEX pipes nestled inside a larger outer pipe. The inner space within this larger pipe is completely filled with foam to minimize heat loss, and this design seems to work well. Water leaving an outdoor furnace at 180 degrees Fahrenheit will only be 1 degree or so cooler 100 feet away, depending on the flow rate through the pipe. The outer layer of pipe is also waterproof, eliminating any chance that the foam will lose its effectiveness by becoming waterlogged.

Working with PEX-Flex isn’t always easy. The version I installed has an outside diameter of just under 4 1/2 inches, and it takes some muscle to get it to bend properly, which made for something of a wrestling match as I uncoiled the pipe and buried it in trenches.

Inadequate underground piping would lead to much less efficient performance for the entire life of the hot water system. At about $15 per foot, PEX-Flex isn’t cheap, but in my opinion, it’s worth the money in heating fuel saved.

Contributing Editor Steve Maxwell has been helping people renovate, build and maintain their homes for more than two decades. “Canada’s Handiest Man” is an award-winning home improvement authority and woodworking expert. Contact him by visiting his website and the blog, Maxwell’s House. You also can follow him on Twitter, like him on Facebook and find him on . 

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