Most things expand when heated and contract when cold and although that's true with water too, water is funny in that when it initially freezes it expands almost 10%. If it gets super cold it will contract again but it has to expand first - and that can cause serious damage if it's contained by something that won't expand with it.
I replaced all of my copper tubing with PEX and PEX will expand more than water will require. However, I have plenty of brass fittings, valves and other elements in the system that will not expand. So it's best to "winterize" an RV or boat to make sure you don't have to repair things in the Spring.
The first step with winterizing is to drain all the tanks. There are two tanks in my Safari, the fresh water tank and the black water tank. The latter is currently always empty because I can't close my dump valve... it's old, stuck open and non-repairable. I'll have to replace it next year if I want to use the black water tank as a tank. Airstreams didn't have grey water tanks until the early 1970's. So there's no grey water tank to drain - but I do want to get the water out of the plumbing traps.
The fresh water tank can be drained by running the freshwater pump until its fully exhausted. The tank could still have some water in it but as long as it's not full, the ice can expand into the empty void. I do want to get the water out of the tube though.
Another tank to drain it the hot water heater. It has it's own drain plug to remove once the system is drained. It's best to include a set of by pass valves int he plumbing system so that you can empty the hot water heater and then by pass it so you don't waste 6 gallons of anti-freeze trying to fill it up.
Once the trailer is drained of water, the next thing to do is to blow compressed air through the lines to push out any water that may be stuck inside. The easiest way to do that is to connect a blow out plug to the city water connection on the side of the trailer.
I bought a Camco blow out that screws on the standard garden hose fitting on one end and has a quick connect fitting for the compressor hose. Since the city water connection is designed for city water pressure of ~55 PSI, I'll set the compressor to 40 PSI so I don't over pressurize the plumbing lines.
The fitting just screws right onto the city water port and then I open each valve inside the trailer to allow the compressed air to blow out any remaining water. Its surprising how much water can still be inside lines that have been "drained".
Every line gets emptied, one at a time, until nothing but air comes out, including the toilet. Then the next challenge is to get RV antifreeze into the system. RV antifreeze is specially formulated for potable water systems and is not the same as antifreeze you might use in your car, etc. A lot of folks may skip this step but I think it's inexpensive insurance to protect against the remote chance there's still water somewhere inside.
There are three ways to get RV antifreeze into the trailer... you can dump a couple gallons into the fresh water tank and use the pump, you can install a FW tank bypass and use the freshwater pump, or you can use a hand pump and push it through the city water connection.
I decided on the latter approach - it seemed the most effective with the least fuss. All I needed was a Camco hand pump. You pump it in while a helper opens each valve until red antifreeze drains out.
Every place where water is intended to come out is operated until RV antifreeze comes out, including the toilet. Then you know there's zero chance of water freezing in the system.
The last step is to pour any remaining antifreeze into the sinks and shower, so all the traps and drains are clear of water too. I also left the refrigerator door open so the interior gets fresh air.
There's also water in the 12V battery - so I'll remove that from the trailer and put it in my garage so I can keep it from freezing and keep it charged too.
A couple of large trash bags will cover the LPG tanks, hose and regulator and protect them from the effects of snow and the sun.
The two tires plus the spare are covered by vinyl tire covers to protect them from UV rays and unnecessary exposure to the elements.
And finally, all the windows are closed and the curtains drawn to protect the interior from UV exposure. I also sealed every exterior seam with fresh Trempro sealant - so hopefully no water will leak in from snow and rain.
Cecil is all buttoned up and can settle down for a long Winter's nap. Sweet dreams, I'll wake you in the Spring!
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