Originally Posted by WavRidr
My plan is to drain the fresh water tank and then pump antifreeze into that and then use the fresh water pump to pump the antifreeze throughout the system
I'm not familiar with your 378FL, but don't add antifreeze to your freshwater tank and pump through system from there. You should be able to add a bypass, if it doesn't already exist, so you can pump directly from the jug of antifreeze. Google/Youtube search on winterizing. As others have said, I've used compressed air for years. Just hook a compressor to the city water connection, google/youtube this as well, takes only a couple of minutes. Then add antifreeze to the p-traps and toilet.