Couple questions: I am making a 8 foot section of 4" pvc pipe into a waterer. I bought some of the yellow nipples on ebay. What can I apply to the pvc to heat the water and be safe for the pvc plastic material? Would it be better to get a bird bath de-icer and make a reservoir attached to the top of the pvc tube with a 4" pvc "cleanout" piece? In order for the water nipples to work, does there need to be a sealed vacuum in the water tank?? I mean does the water tank need to be closed or can it have an open top (in which to drop in a bird bath de-icer)?