Subject: Plumbing, Other Than Toilets (5/27/1993)
[5/27/93] We are all familiar with copper tubing and the fact that it bursts when it freezes. Many years ago Peter Robins experimented with plastic braided tubing (approximately 1978 as I recall) and found that a certain kind would not burst when water froze in it, instead the tubing simply experienced some localized swelling. I believe that Brett Eisele wrote an article about this which appeared in PV several years ago, but he did not specify the type of plastic. Amtrak is also using braided plastic tubing, and I remember that Ed Laird and Elton Miller told me that you could fill a piece of this tubing with water, put a plug in each end, put it in your freezer, and it would not burst. I remember from college chemistry, or was it physics, that water expands to its largest volume at 34 deg. F., just before it freezes. Thus, the critical point for freezing in pipes is not when it is frozen, but just before it freezes, when the water swells.
In any event, Elton sent me a piece of tubing which Amtrak uses, and I then went to my local Builder's Square and Home Depot stores, and found that the same tubing is available, by the foot, at both. The tubing used is clear flexible PVC tubing with nylon braid. Do not use urethane tubing, as it is gradually attacked by water. The Home Depot thickness is not quite as great as that which Amtrak uses, but in my experiments in the deep freeze, it did not burst, nor did nylon connectors burst either. Apparently the tubing will give enough to offset the rigidity of the nylon connector. You may wish to consider this for your plumbing needs, although I have no idea how it will stand up next to heat tape.
Paul L. DeVerter II
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