My house has no water pressure in all of the upstairs Bath/Sink/toilet, the downstairs bath tub has pressure... but the downstairs sinks and toilet have no pressure. We are finding little black particles coming out of all of the household fixtures. We believe the source may be from the water softener, the main line from the city water before going into the softener is clean of particles, but the water faucet right after exiting the water softener has particles. We have now bypassed the water softener, but the house water pressure is not restored. How do I get the rest of the particles out of the pipes?

"how do i get the rest of the particles out of the pipes?" You shut the water off at the stops and flush the valve, branches and supplies out one by one. Good luck, Tom