I had a radon mitigation system installed in my house prior to
purchase. The other day, while doing some sealing in the attic, I
noticed that they have the radon PVC pipe running right next to the
water heater flue to get from the basement to the attic. You can see
a couple pictures he

http://www.msu.edu/~galedav1/pic1.jpg
http://www.msu.edu/~galedav1/pic2.jpg

Is it OK to have the radon pipe running next to the water heater
flue? I checked with the city, but they claim the code only says to
"install per manufacturer's instructions." Elsewhere I have heard
there should be 2" of clearance between the flue and anything
flammable. Is the PVC pipe considered flammable?

Thanks in advance!

Dave