do you know if there is a accumulator in your system? A lot of systems have an expansion tank (accumulator) to prevent excess pressure or a back flow. They usually look like a propane tank (a residential one would usually be about one half the diameter of a standard 20 pound grill tank). the way the the work is they have a rubber diaphragm to hold pressure in the system. This diaphragm eventually fails and the tank must be replaced. When the diaphragm pops it shocks the system jarring loose scale and black oxide from the backside of the diaphragm releasing black water. I have only seen it happen one time but when the diaphragm popped a small shred of it washed out into the connector pipe and blocked the flow of water to the whole house. If you turn off the main water supply and then unscrew the tank from it's connection and then briefly turn on the main water supply and clean water flows from the open connection then maybe you have a piece of the diaphragm blocking down line. Hopefully it will be right there at the connection and you can dig it out.
NOTE make sure the water that sprays out when you run your test can be caught or mopped up quickly so it won't do any damage
good luck bruno
bruno
May 2008
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