My brother in law called asking for help replacing a couple of leaking water valves in his basement supplying his kitchen sink.
I loaded my plumbing buckets into the truck then went out to the pipe rack in the barn to cut a few feet of 1/2" copper tube. Beneath the rack was about a 3' length of fairly shiny 1/2" that I didn't recall cutting off, but since it was already there and cut, I grabbed it and went off to tackle the half hour job, which for once, actually took only a half hour.
The following day, my BIL called me reporting when he ran hot water in the kitchen sink, it smelled like oil or gas. Huh? He repeated his statement. The only items changed were the 2 stops which he provided, 2 short lengths of pipe, and 2 connectors which I provided.
I went out to recover the foot or so of pipe that was left over from the job laying in the back of the truck, looked at the inside and sure enough, it appeared to be darker than normal.
A sniff test indeed indicated a petroleum smell. A pencil and paper towel swab deposited a black oily looking substance on the towel. I called my BIL back advising him not to drink the water.
That evening with another length of pipe off the rack, this one examined and determined to be suitable for use with potable water, off I went to re-do the job. Upon completion of what I had done the previous day, the end result after thoroughly flushing the flux out, was no evident smell or taste of contamination.
The next day with the whole family at the house, I began interviewing suspects and it wasn't long before I found the culprit.
My youngest son and his buddies from down the road were messing with a quad deciding a need to improve upon the quality of the factory exhaust and its sound. They attempted to utilize the copper pipe they boosted from the rack and when unsatisfied with its performance, cut off the end they had screwed up returning the leave over to the rack, which later fell to the ground I imagine.
After explaining my ordeal, my son first apologized then questioned why I didn't look at it or smell it before I used it... I didn't think I needed to taste test brand new pipe I had purchased in the past, warehousing for later use on a rainy day.
Had the basement not been dingy and dim, I may have noticed the discoloration inside while fitting the outside, but smelling it before use? Out of the question.
So it seems the lesson learned is if you allow others access to your stock, perhaps it is a good idea to exercise a little extra caution before using materials others have had their fingers on.