The pipes in my place are made of either PVC and Copper, now the temp outside is close to 22f, and obviously one of my PVC pipe is frozen. I am worry about the pipe may go bursted.I believe I once heard someone said that PVC pipe is in fact stronger than copper one and the chances for PVC pipe to burst is relatively low. I wonder if it‘s true that PVC pipe is less vulnerable?
You do not indicate the sizes of the piping in question, nor what the rating was for the PVC pipe initially installed. This may have some bearing on the method of repair because copper is now very expensive and SCH 40 copper pipe would be both difficult to find and exceptionally expensive if you did. Also, copper is already an extravagant material to use on chilled water piping (not small tubing) when flanged and welded Sch 40 carbon steel is the most commonly used material in larger sizes and screwed galvanized pipe is used for most 2 1/2 and smaller. PCV pipe needs to be supported more frequently than steel pipe and will have a much lower service pressure rating. However, your operating pressure may still be within the allowable range. At these service temperatures, thermal expansion is not going to be a problem regardless of what materials are used. If your ONLY problem is that some joints leak, it is probably because the surfaces were not proplerly prepared and/or the cement was not allowed adequate time to set before the piping was moved around. I would recommend that in this case you forget the copper ( forever) and investigate the cutting-out and proper replacement of the several deffective fittings with CPVC Sch 40, piping and equivalent solvent joint fittings.
Often PVC piping is used for drainage and copper for supply lines. If you had PVC and copper pipes with the same inner diameter, correctly fitted joints and water inside at the same pressure levels, the PVC will burst first as the water freezes. In a drainage situation, there is a lot of air in the pipes -- and thus provides room for water to expand (as it freezes). So, there is a lot less threat of a PVC bursting. If given the choice of piping, nowadays. go with the new PEX piping. Cheaper than copper and has a greater strength than either PVC or copper due to the fact that it (PEX) can expand and contract. If you find yourself in a situation where you are concerned that pipes will freeze, the best thing to do to quickly rememdy the situation (until you can restore heat) is to turn on of your faucets on to a trickle. As long as the water is moving, you'll be okay. Good luck.
