One of my bathrooms hot water pressure is low to a trickle. When I took thetub faucet of I found gray/black goop in the faucet pipe. A year ago we had the waterheater element replaced in our oil furnace because it fell apart. Now I think the particles are blocking the faucet in the last bath on theline. How do I flush out the line?

one of my bathrooms hot water pressure is low to a trickle. When I took thetub faucet of I found gray/black goop in the faucet pipe. A year ago we had the waterheater element replaced in our oil furnace because it fell apart. Now I think the particles are blocking the faucet in the last bath on theline. How do I flush out the line?
You first shut the water off to the faucet in question and open it up to remove the cartridge, Check and clean then inlet ports. Now place a p[an over the open valve and turn the water on to flush out the lines. You should have a strong stream when doing this. If not then click on back and tell me. Good luck, Tom