The black water does not come out all the time. When you first turn on the water it is black. Is there any way to stop it?
Sounds like your pipes are starting to corrode, the only way to stop the black water is to replace the pipe causing it. When the water is off the black corrosion builds up and when you turn the water on it all comes out at once, when the water is running there is still black coming out but is a small amount that you cannot see or do not notice.
Find the master link and take it apart to remove chain. Replace when ready.
Hey Buddy, If you have copper pipes, it will be corrosion. If it's plastic pipes you shouldn't have that problem. Replace the pipe and get rid of the black stuff. Sometimes, when you replace your water lines you will have some dirt or trash come out of the faucets for a few seconds until it clears out. Running your water for a minute or so should get that out. If you need help, just let me know.