I have 12 volt surface mount cord connected submersible fixtures I'm installing in the side wall of a fountain.the fixtures will be under water.My question about the piping.there are 20 lights and would like to run a pipe from each fixture through the gunite from below the light out the back of the fountain,all below water.Do I need to seal the end,Can I use electrical pvc?The head is removable from the base plate for relamping.the cord is connected the head. Thanks.