Dirt coming out of my shower!!!?

you are better off letting the water run through the bath spout versus the shower head until you no longer see any grit in the water. This grit is due to the disturbance of the piping and water heater replacement. Also the loss of water pressure in your bathroom sink is due to this grit clogging up the valves within the faucet so to fix this the valves will need to be removed and cleaned out and after removing the valve flush them with water, reembly and allow water to run until no grit is present in the water.