Is It Necessary Or Advised To Drain My Water Heater Periodically, To Prevent Rust In Bottom And Eventually Leakage, It's A Gas House Water Heater. My Plumber, When Installilng It, Said It's Not Necessary, But Maybe He Just Wants The Business.

You shouldn't need to drain the entire tank, but it wouldn't hurt to periodically hook a garden hose up to the boiler drain at the bottom of the tank and flush it out for a minute or two.