I am a homeowner and live in a house built in the 1950's. When I run a bath, and only a bath it seems, I occasionally get varying sizes of black particles in my bath water. As long as I do not touch these particles they will float around in the water in one solid piece. However, if I touch them, they turn to what looks like "powder" floating in the water, until they dissipate. I can trap one of these particles under my finger and actually write on the bottom of my bathtub as if I was writing on paper with a pencil. A black powder will float up around my finger as I "write" on my tub, and it will stain not only my finger for a time, but my bathtub for life it seems. I have asked many people about this and no one- including my utility company- seems to have any idea what this could be. They are all recommending that I get a water sampling kit and mail it into a lab to test my water for whatever mineral this is that is causing this. I am not too concerned, I live in an older house, but I would like the peace of mind to know that its not lead that I am rubbing around with my finger in my bath water! I was hoping that someone here might know something of this or have heard of something like this and could direct me on this matter before I pay the $40 to get my water tested. Thank You!
You do know that this is an unusual problem, right?
How old is the tub valve? is it possible that you've got disintegrating rubber parts in the tub? It sounds like old neoprene rubber. It's also possible that there's an old bit of rubber that fell off a valve somewhere in the house. I'd take the tub valve apart (after turning off the water) and try turning the water back on long enough to flush the valve out. With the rubber parts removed from the valves, if you still get flakes, it might be in the pipes.
There have been problems with rubber-lined water heater flex connectors.
Steve's Plumbing Service