Replies

1. 
   Danno | Mar 21, 2009 03:29pm | #1

   I ran into a similar problem once and looked and found that apparently the plumber had run out of (in this case) galvanized pipe and did the last short nipple in the spout with black pipe and so it rusted. Maybe somewhere in your supply there is some black pipe? Another thing to look for might be dissimilar metals--like a connection of copper to galvanized without a dielectric union.

2. 
   DanH | Mar 21, 2009 03:46pm | #2

   Yeah, most likely there's a mixture of iron and copper pipe feeding the tub. What you're seeing is essentially rust caused by electrolytic action between the dissimilar metals. Harmless in the near term, but eventually (in ten days or ten years) the iron pipe will rust through.

   The modern conservative is engaged in one of man's oldest exercises in moral philosophy; that is, the search for a superior moral justification for selfishness. -John Kenneth Galbraith