What's That Black Goo?

[velvetfoot]

I took apart a vent valve this afternoon and saw a lot of black goo in there. I've seen the same thing when I did some plumbing work on a cold water line. It doesn't clean off with soap, but did with a citrus based solvent. We have well water, but it's not that hard and we use a softener. I figure it's bacteriological. We do get a whiff of sulfur every once in a while in our drinking water, but nothing much.

 

[Boil&Toil]

While it could be black sulfur, there's generally more than an occasional whiff when you have that problem. Most likely IMHO for a boiler system is one of the black forms of rust, since the method used to deal with oxygen in the water used to fill a system with iron parts is to seal it so no more oxygen gets in, and let the system rust out whatever oxygen is dissolved in the fill water. Without excess oxygen, some of that rusting will result in black rather than orange rust (I can't recall the specific oxides at the moment, but there are several variants.)

 

[MarkW]

I get it too. Mineral eating bacteria, is what I've been told. If I don't filter/soften the water, it's almost unpalatable.

http://www.water-research.net/iron.htm

This says it's manganese

 

[Bob Rohr]

I get it too. Mineral eating bacteria, is what I've been told. If I don't filter/soften the water, it's almost unpalatable.

http://www.water-research.net/iron.htm

This says it's manganese

Could be iron bacteria if it is in the drinking and boiler water. Iron bacteria can eat away at the steel well casing as well as any ferrous component in your hydronic system. it can be tough to get rid of and flush from the system. deal with it as soon as possible.

if it is magnetic it could be iron ferrite caused by o2 getting into the system.

 

[MarkW]

I should note that I didn't use my well water in my boiler. It was faster to bring it from work in a water trailer.

 

[Fred61]

This says it's manganese

That's exactly what it is. Your clue was "mild sulfur smell".

 

[velvetfoot]

Thanks everyone.