GE GEH Series Service Manual page 66

If flushing the tank, disconnect power but leave the water
supply turned on. The flow of cold water into the tank
helps to stir the sediment at the bottom and force it out
the drain hose.
If replacing a heating element or pressure relief valve,
disconnect power, turn off the water supply and open a
faucet somewhere in the home. Drain the tank to the
appropriate level and make the necessary repair.
NOTE: When flushing or draining the tank, always allow
water to flow for several minutes at a tub faucet after the
repair. This will help to purge any air from the system
and remove any stirred-up sediment which could clog
other home faucets that contain screens.
66