Chlorinate hot water heater
If I were to add chlorine to a water heater I would add it through the anode port, this would be a good time to verify that the anode is still serviceable. After letting the treated water sit I would flush through the closest hot water faucet and once the majority of the strong chlorine is gone flush all the hot taps to prevent chlorine poisoning. My well guy told me of a family that saw him bleach the well and did not realize he flushed the well for 3 hours after waiting 3 hours. Almost killed 2 or 3 of them. So be careful and flush the tank until almost no smell.