Want to replace sink drain to pvc. P trap going into wall won't be changed. Is that curved piece an S bend? Are these pretty standard items HD should carry? Since they use compression fittings, sealant isn't necessary, correct? Is there anything I can do to protect the threads on my large pipe drain from corrosion? Welcome any other suggestions I may be missing. Thank you. [url]https://imgur.com/a/gzxL0fH[/url]

Hello, I noticed signs of moisture on the outside wall of my house, just a few inches above the PVC drain/access port. On the other side of that wall is our tilled shower. Note that the hot/cold water pipes are not on that wall but on an adjacent wall (90 degree of that outside wall). the dark/moist area is roughly 8x8" - and other than for that shower drain there is no water pipe in that wall at all. Before we go ahead and start tearing apart stuff, I wanted to hear from others about the likelihood of the leak coming from that drain pipe itself or if it could be from maybe a non proper job on that custom shower. I'll take care some pictures later, but there is no sign of leak/damage anywhere on the inside walls/shower itself. the tile grout joint is not dark or doesn't have any obvious sign of mold developing underneath (on the walls or the shower floor). If it wasn't for that dark spot on the outside I wouldn't suspect any leak whatsoever. thanks you