PVC piping was utilized on one of our project for chilled water piping (42-56 degree). it appears there are leakegaes at the joints. could you tell me how we need to install PVC Sch 40 pipe to copper pipe without any leakages. or why connection leaks? I need some Tips Warnings.
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.
Like a hot water system, chilled water will go through thermal cycles. As the pipe alternate between being hot cold the PVC and copper will expand and contract. The problem here is that plastic and metal expand at different rates. If you use male and female threaded adapters on each type of pipe you will join them together, but the joint will eventually leak. The different amounts of expansion of one material threaded into the other will cause the thread of the softer material to deform thereby loosening the joint and causing it to leak. Threaded adapters are for adapting un-threaded pipe to a threaded connection of the same material. Like a PVC pipe into a PVC filter housing that has threaded connections. To connect metal pipe to plastic pipe you need to use a special fitting designed for the job that can handle the different expansion rates and maintain a seal. There are two basic types, a transition union or a Copper to PVC adapter. Each type allows some mechanical movement due to thermal expansion while maintaining a water tight seal.
