I have standard 1/2″ copper solder fittings, can I use 1/2″ compression fittings in its place?
” Probably not. In the plumbing trade when we say 1/2″ soldered fittings we mean fittings that use 1/2″ nominal pipe (which means 5/8″ outside diameter pipe). To figure what size pipe to use with “standard” solder (not compression like those above) plumbing fittings, you must add 1/8″ to your measurements to know the o.d. (outside diameter) of the pipe. 1/2″ nominal fittings use 5/8″ od pipe; 3/4″ fittings uses 7/8″ pipe and so on. It can all be confusing. The above compression fittings use the outside diameter of pipe, so a 1/2″ compression fitting uses 1/2″ outside diameter copper pipe. “Standard” plumbing terminology with copper solder fittings use “nominal” pipes but not so with compression fittings. That means a “standard” 1/2″ soldered fitting uses the same pipe as 5/8″ compression pipe. For above compression fittings simply measure the outside diameter of the pipe and that is the size of the compression fitting that you should order. 1/2″ outside pipe means you need to order 1/2
