[TheSrProgrammer]

What is the best way to disconnect the drainage pipe shown in the picture? If I have to cut something, what's the best way to deal with reconnecting, especially with shortened pipe length? It never made a whole lot of sense that a lot of times the best way to take PVC apart and put it back together again is to cut it and then be left figuring out how to put it back together with one piece obviously shorter than it was originally. It is a seemingly unnecessary headache... One would think there is a better way.

 

[TheEplumber]

I'm not sure where you want to disconnect, but the nut at the base of the tee (tailpiece nut) will unscrew and it should unscrew on both ends of the trap

 

[TheSrProgrammer]

Is a channellock the best tool for this? I'm attempting to disconnect the utility sink to pull it out and remove that drywall behind it. There was a leak there years ago, and apparently the homeowner didn't think that would cause mold growth... But it did. See the picture of the other side of the wall.

 

[TheEplumber]

Channeloks will work good, provided they're large enough.
Be prepared to replace the nylon gaskets it the nuts- they're priced cheap. Also, you could replace the tailpiece with an economical plastic one too. The chrome one might be about worn out