Next time just blow dry the line. Use a oil-less compressor so as not to contaminate the water lines. That is the procedure that Lazy Daze recommends in their owners manual. I do not have the book in front of me but as I recall it is roughly something like this.
... open all fresh water faucets
... dump fresh water tank,
... dump hot water tank, put the plug back in the hot water tank (I sometimes forget to do this and it slows me down in later steps)
... On the out side of the RV press the purge valve at the city water inlet. You want to do this step when there is no pressure in the water lines.
... disconnect water pipe at downstream side of pump
... close all water faucets
... remove the aerator from the faucets (not one of LD's steps but it will prevent clogging when you refill with water).
... connect air hose to the water system (they sell a hose that will screw into the water line at the pump connection, but I am sure it is available else where)
... run the air tank out line at 50#. This is about 10-15# less than the water system rated for. You might want to check what your system is rated at.
... slowly open the highest faucet (kitchen sink in my RV)run until air comes out. Do the same with hot water. Make your way to each water source and do the same. It takes a couple trips around the RV until all the gurgles are gone. The trick is to only open the faucet a little so the water is pushed as a body.
... empty the pump and strainer of fresh water. (I just turn on the pump and let the pint or less of water run onto a towel).
At this point the OP's water lines should be good for the 25 deg weather. I run pink stuff through the strainer and pump while the line is off the water pump (just look for pink stuff on the towel.
... reattach water line to pump.
... empty black and grey tanks
... pour antifreeze in each sink, shower, and toilet.
I tend to use a gal for the complete process because I want a fair amount of antifreeze in the bottom of each tank. I keep a gal in the RV to flush the ptraps and put in the tanks in case I want to camp in the winter.
It took me almost as long to type the procedure just now as it did to blow the lines (discounting dumping all tanks).
I do not think I would ever put antifreeze in the fresh water tank. You might want to consult a pro on how to make sure there is none left in the system.