That "white crud" is actually sulfur that's eating away at your flue pipe
and chimney. It should be going out the top of your chimney with the flue
gases. Your heater stack temp is probably too low. IMO, a net stack
temperature should be no less than 325 degrees F, and preferably at least
350 degrees.

"mm" wrote in message
...
On Wed, 11 Jan 2006 19:38:55 GMT, "Art"
wrote:


My cap blew off, and blew off again after reattached. Didn't get it
replaced for a few months or more, and white crud started coming out
of the seams where the flue bent around to go into the chimney. I
guess it was a mixture of water and soot and something else.