I'm an idiot! - Bathtub drain pipe question

Hi everyone, first post here. Looks like a great forum and happy I found it.

I'm in the midst of installing a bathtub, and for reasons I can't explain, I measured only once (ugh) and cut the brass tail (drain?) pipe too short. Can I extend the pipe by soldering on a coupler/union, and if so, what kind of coupling am I looking for? I purchased a 1-1/2" copper coupling for the bath drain pipe (1-1/2" OD) but it's entirely too large...clearly I am missing some very basic knowledge here. A short length of brass pipe with threaded ends that could be used with slip nuts would also work, but I don't know if such a fitting exists. Or do I need to buy a whole new assembly because of my stupidity?

Sorry for what I am sure is a very naive question - I'm an advanced DIYer in everything BUT plumbing. I appreciate the help!

 

There probably are tubular drain fittings you could use, but you're not likely to find them outside a specialty plumbing outlet if you insist on using
brass (a very old-fashioned and expensive way to go). Slip-joint extensions as short as 4" are available. Tubular drain pieces (such as you are using) do
not mix with copper DWV (drain, waste, & vent) items except via the use of special adapters. Similarly with Schedule 40 plastic and galv. steel DWV
pipes. Dimensions in each of those systems are "nominal".

 

There are tailpiece extensions for tubular drain pipes available - I think I've even seen them at a big box store, but more selection available at a plumbing supply house. These usually come with a beveled compression washer and a nut to make the seal.

 

Thanks guys. I picked up a tailpiece extension at the big box store. Did the trick.