Originally Posted by HowieE
Just pumping in antifreeze is not a good idea. You should blow down the system from the city connection first. Drain the hot water heater and switch to bypass mode, if equipped. Then remove the input line to the pump and use the pump to fill the system. Failure to do this will leave water in the line from the city connection to the rest of the system. If there is not a bypass valve on the trailer you should consider putting one on before you travel. Failure to do this will require 6 gallons of antifreeze and no guarantee you had done more than just dilute things.
If the day time temperatures are above freezing while traveling and the nighttime temperature are above 25F you can safely do nothing. It takes more than an overnight to freeze things up at those temperatures.
There is nothing colder than an Airstream trailer if you come out of your truck and step into an unheated trailer. Radiating to cold aluminum is like sitting on dry ice. Use the heater.
I have done it both ways over the years - i.e. blowing first with compressed air, then pumping in the antifreeze or just pumping in the antifreeze to pump out the water. Never had a problem with either method, and it does get pretty cold up this way!
As for the incoming city water line, you make a good point and no doubt your method is the surest.
In our case, ours has an external tap right near the city water inlet - I do always crack that open until it runs pink. I guess that is why I have never had a problem with it when I have not first blown the lines with air. I also crack the two low point drains open momentarily.
To the original poster
To make the job of filling the plumbing lines with antifreeze as easy as possible, you need bypass valves on your HW tank allowing you to take the HW tank out of the system and just drain the water out of it leaving it empty.
To get the antifreeze into the system, the easiest way is to have a short suction hose on your 12v
pump inlet. You disconnect the pump suction from the fresh water tank, then use the short suction hose to suck antifreeze directly from the one gallon jugs into the plumbing system.
Once ready to start the process, you then go around opening ALL hot and cold taps one at a time letting them run until they run pink showing that the antifreeze is escaping. Don't forget the galley sink rinse hose, shower, and toilet rinse hose if there is one.
Normally takes about a gallon on a half when I do this with our Classic 30.
I dump the remainder into the sink traps, shower drain and toilet bowl to ensure they are protected and to keep the seal in the toilet soft and working.
The whole process takes me probably twenty minutes.
It is possible that your trailer might need to have an HW tank bypass installed, and also a means to allow your 12v
pump to draw from the jugs of antifreeze.
Any RV shop should be able to attend to these items for you if needed.