My cold water lines have sediment in lines from old water heater. I replaced water heater need to know how to flush cold water lines , I have very low cold water pressure. You can see sediment in lines causing low water pressure.

To begain with I wouldn't "backflush". I'd flush the branches out on a fixture by fixture basis. How you do this is by turning off the house shutoff and unscrewing each cold water supply angle stop. Place a bccket in front of the open stubout and turn the pressure back on until the water runs clear. Do this with each fixture affected. But you may still have a problem even after flushing the lines. If there's still a problem the faucet aerators and cartridge inlet ports might still be clogged. You will then have to go back and open up and check and clean the valves. Good luck, Tom