Thawing frozen water pipes?

When you get the dripping you need to leave the faucets on even overnight in order to keep the water flowing. The hole where you have the heater is somewhere after the freeze. see if you can follow it back some. It probably goes near an outside wall which is why it is freezing. Once you get it thawed put a low expanding spray foam in the cavity around the pipe to keep it from happening again and again, and maybe bursting the pipe.