My house was built in 2000 and has a well. The previous owner didn't
have any type of filter on the water and there was a hydrogen sulfide
problem that I eliminated with the install of a backflushing pyrolox
whole house filter. Water quality is fine now and no issues.

My problem is that whenever I shut down (only a few times) the water
and drain the system (faucet valve repair, moving pipes for
remodeling) and then start the water back up, I get this black stuff
coming out of all the faucets for a few moments...it almost seems like
a grease of some sort. Well I just had to relocate some pipes and I
notice that the insides of them are coated with this stuff...not a
large buildup, but the entire interior of the copper pipe has this on
it. I have noticed this everytime I cut into the plumbing. I am
assuming it is from the pre-filter days. Anybody know how to get rid
of this stuff?