DIY Hydronic Floor Heating

[AC_Hacker]

Originally Posted by Piwoslaw

I could not find anything about what type of tubing to use or what diameter (I assume there is only one standard diameter?).

Piwoslaw,

Thank you for posting this info.

I'm still learning how designing with PEX works, too.

But I can answer your question about PEX diameter.

PEX comes in many different diameters.

In the USA, (and Canada too I assume), the PEX OD sizes are:

• 3/8"
• 1/2"
• 5/8"
• 3/4"
• 1"

I would guess that in Europe (where PEX started) PEX would be made to even metric dimensions, and that the step sizes would be roughly equivalent to the list above

The following notes primarily apply to PEX radiant floors...

NOTE 1: The 5/8" size is made, but not often stocked. If a design requires it, it can be found. Also, PEX sizes can go mich larger than 1". I limited the list because most PEX residential heating jobs would not usually require it.

NOTE 2: Assuming equal pipe spacing, the diameter of PEX does affect the amount of heat given off per unit area, but less than one might think. I found an excellent article by John Siegenthaler, the guy who wrote the bible on radiant heating. Here's a chart of various diameter PEX schemes:

The article is the best of its kind, should be read in its entirety.

He also did an article called Depth Perception, which addressed the optimum depth of PEX tubing in a slab.

Regards,

-AC_Hacker