We seem to go through this discussion every year.
Antifreeze is not used to protect the plumbing. It is used to flush out the water, the only liquid that expands when frozen.
Once the lines have been filled with antifreeze and flushed out the water it's perfectly ok to drain it into a bucket and use it to fill all the P traps. Antifreeze and water mixed 50/50 will freeze into a soft slush but will not expand enough to do damage.
I've been winterizing my cottage for 35 years, all copper pipes, no problems using this method and it always gets to -30F for a couple of days in Feb.
