hello all,
i am building a new house with in floor radiant heat.
we would like to run the pex tube in shower pan also.
has anyone done this???
Above or below the PVC liner???

Yes
Forget about the liner and build your mortar bed around and over the tubes. You'll need to have the thickness of the bed at least 1-1/4" thick above the tubes. Waterproof your showerpan with Kerdi membrane.

I sure wasn't expecting that.
Have you done it this way before??
would the pvc liner degrade over time?
Thanks

Yes I have done it this way.
It has nothing to do with whether the pvc liner will degrade or not .... the solid waterproof membrane (kerdi) over top the mortar bed is just a better system.

But if you're more comfortable with the conventional liner that system will work fine also.

This page may help. I didn't get a photo of the tubes on the shower floor before the mortar bed, but did get photos of the tubes running over top the bench.
http://www.ontariotile.com/ceramic-tile-bathroom-9.html

Harry,
Great info- great site
thanks for everything.
Dave