Under my kitchen sink the pipe that is CURVED has white spots all over it and white substance attached to it. It is not leaking or anything. Should this pipe be replaced and what is that exactly. thanks. It is not a PVC Pipe. It's stainless steel.

I doubt stainless steel. If so, it most likely wouldn't corrode. Probably chromed brass. Yes, just get a PVC trap.

If you dampen your finger and rub the spots do they totally disappear? If so, not need to replace but tighten the nuts a bit, you have been dripping.

Hi Forever

The pipe sounds like it may be an old galvanized PTRAP (water is always present in the PTRAP to keep sewer gasses from coming into the home). If it isn't galvanized then it is an older style brass PTRAP. Either way, I would NOT advise you to touch this old pipe or tighten any nuts (sorry Bob) as you could tighten something and start a major leak that could require replacement of the PTRAP and more piping. Basically, as is the case with most old plumbing, if it ain't leaking, don't touch it!!

Good day!

Mark

No problems Mass. My question is yet unanswered by the poster but if those spots wipe off clean it's likely Lime from a slow drip.