If you use duct tape, the ice will push the tape off before splitting the pipe. If you want to split the pipe, seal it off better. But really, 10 wraps or so, both across and around it, stretched and tight. You are attempting to seal water with duct tape, NEVER works in plumbing, but it could leak out into the freezer! A header pipe, could freeze in 5 hours, an expansion chamber 8. Check it every once in a while. Normal freezers are around 0 degrees fahrenheit. Deep freezers may differ. One word of caution with stamped pipes, be real careful with them. Titanium, stainless and welded pipes are pretty strong. Stronger than duct tape!