When I go on a winter vacation cruise, I drain my pipes at the basement water tank valve.
I open all valves to vent.
Question: Is that enough precaution? I had no trouble. If my furnace heat quit would it be ok?
If water does freeze in a pipe that, for example, has a u shaped curve in it; albeit mostly empty, will the U shape split?
I hope the answer is no, the ice will slide along harmlessly provided the pipe is mostly empty.
Does anybody have knowledge of freeze and pipes?
What else do people do?

yes the pipe will split if it freezes hard. if the house temperature drops just below freezing by a couple of degrees the water will turn to slush rather than hard ice and not cause any damage.
there are lots of simple things that professionals do.
one is to blow air into the pipes to force the water out of any low spots.
another is to pour RV antifreeze into an open faucet and let it find the low spots.
so much depends on how your house is piped..

What happens when water freezes depends on HOW it freezes. If the two ends are open so the ice and water can expand longitudinally, nothing may happen. But if the ends are plugged, or the water is trapped between two ice areas so it has nowhere to go but outward, it will probably break.

Based on what my friends are saying, and my evaluation, I think that draining all pipes via the lowest point and vent all lav faucets would accomplish the no blockage theory. But there is an element of uncertainty due to dips and corners of piping. Many odd things happen in this trade.

I suppose to be sure I would have to fill all pipes with rv antifreeze and be sure all puddled liquid in any low spots of the copper plumbing were filled with antifreeze without any diluted areas. That would involve some suction process at the highest point in the plumbing, to draw the antifreeze in, I surmise.
The air blast sounds good, but could (would) allow water to trickle back and possibly fill some areas, Yes?

I bring the subject up because some houses were winterized during a real-estate stall, and there were burst pipes for the new buyers. I do not know what their process was! Not good!!

For a test I should make up some pipes with U shaped dips and T fittings all filled at about half to see what happens in a freeze. Where I am at it got to -21F during my vacation. My furnace never skipped a beat, but the house was set to 60F while away for three weeks. Record lows.
Thanks for the inputs.



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