We have an upstairs bathroom that we've gutted and are having some contractors remodel. The toilet is the only thing that hasn't been touched. We had a plumber come and redo all of the source and drain lines for the new sinks and the shower. The other day, he turned off the water for the entire day to do his work and turned it on when he was done.
That evening, we turned on one of the downstairs baths, and blue water came out for about 2-3 seconds, then it became clear. We tried other sinks and saw the same thing. My immediate fear was that this was somehow the water from the blue bleach tablet we had in the upstairs toilet and that somehow the sewage drain line water from the toilet was making its way into the source line. I'm no plumber, but this seemed improbable to me since they are separate lines and direction the water pressure would probably not allow it to go throughout the entire house the way it did.
The plumber is a trustworthy guy who has done a lot of work for us before. He was pretty astonished when I showed him the blue water coming out of the downstairs bathroom faucet. He rechecked the lines and felt that it was unlikely that the sewage water was getting into the source line, but had no solid explanation for the blue water. He said it could be that the source valve for the toilet tank was somehow letting water back into the source line, but he seemed skeptical. He also said that it could be a coincidence of timing and that maybe the city's copper line has some corrosion which could possibly cause blue water. He suggested getting the city to come check the water quality.
We caught some of the water in a glass to see how blue it is. I apparently can't seem to smell anything, but my wife assures me that it smells like the bleach tablets. We we're going to try to put some food coloring of a different color in the toilet and see if that color comes through. We're also going to experiment with whether it happens only after we flush the toilet.
Any other suggestions? Has anybody seen something like this before?