[A/S] How cold is cold?

["John Hilty" <hilty@xxxxxxxxxxxxx>]

This weekend I blew out my water lines with compressed air and did 
everything I have been told to do to winterize since we are told to 
expect an arctic cold front through the Dallas area tonight. The temp 
will probably get into the mid 20's and could stay there for as much 
as 12 hours or so. I know that this is not very cold in relation to 
the way things are up north. I've lived there and I am familiar with 
long periods of sub zero weather. Since we don't get that much 
freezing weather here and when we do it is of fairly short duration, 
my question is how cold and what time period would it take to freeze 
water lines that are full or partially full of water. Since we like
to do winter camping it is a pain in the a** to go through the 
clearing the lines routine routinely. Any thoughts?

John H.