How do you remove/replace a plumbing fitting that is threaded on both sides when they can’t rotate?

Question

I feel like a bit of an idiot for asking this question because it seems like there must be a simple answer to this, but I can’t quite figure out what it is.

Let’s say I have a check valve that is threaded on both ends.

And let’s say I’m using some copper press fittings to attach it to copper pipe.

So I screw those fittings onto the ends of the check valve, then press the fittings onto the pipes to finish the connections.

Check valves don’t last forever, though, and at some point it might break and need to be replaced. The fittings don’t rotate so you can’t unthread them from the check valve, and the check valve can’t rotate because loosening one end tightens the other end.

I could cut the pipes where they enter the fittings and toss it all out, but now I’ve lost pipe so a new check valve and fittings won’t be long enough to press back onto the pipe ends. So I guess now I need to cut the pipes back further and introduce more fittings and pipe to get the pipe back to the original length?

Is that the only way to replace a threaded part in this scenario? Or is there some other part/fitting or way of doing this that’s better?

Thanks!

Answer 1

You provide a union, or use fittings that can act as a union.

I'm not sure about those "press fittings", I've never used them, but PEX crimp fittings will turn without leaking after crimping, so they "act as a union"- but the default answer for threaded fittings in general is a union, which is specifically designed to be loosened without anything (other than the union nut) needing to turn, so that you can disassemble things that do need to turn next to them.

Flanges are another option - common on heating system circulator pumps, rare in normal household water plumbing.

Third option with copper is to use a solder joint that can be removed non-destructively. I believe (but also don't use them myself) that SharkBites will both rotate, and can also be non-destructively disassembled.

Answer 2

Hopefully it will outlive yo and this question is moot.

Either use a union, or you can use slip joint or a coupler without a stop.

Sharkbite makes a decent slip joint product -- you cut the pipe, slide it over several inches of one pipe, and pull it back to 'bite' the other pipe.

Alternatively, there are copper sweat fittings that slide over one pipe, then slide back over the other one and can be soldered in place pretty easily.

Here's a picture: