The tube must terminate no more than 6 inches from the floor or be directed
to the exterior of the home.

Notice this one says six to twelve inches above the floor:
http://www.factsfacts.com/MyHomeRepa...sureRelief.htm

And, again, note the restrictions on the materials.

The discharge tube overflow pipe "must be made of a material that's rated
for both high temperature and pressure. This includes most rigid wall
copper, iron and, in most places, chlorinated polyvinylchloride (CPVC
plastic not regular PVC) pipe. The pipe size must match the opening size
of the TPR valve discharge (usually ¾ inch). It must terminate 6"-12"
above the floor, and the end cannot be threaded or have a fitting which
permits connecting a plug or cap."