Old inlet leaking....help please!

[Smoky]

Can any clever plumber type person tell me how I can repair this water inlet contraption? I have an old metal water tank that was designed to be pressurized with air but I don’t use it that way, I have a 12 volt water pump. This past year whenever I would need water I would just turn the water on at the rv park for a few minutes until water would start squirting out around the inlet. I wish I could just leave the city water on all the time so I wouldn’t have to fill it up everyday. I would just soon repair what I have instead of buying a plastic water tank and new inlet. Any suggestions? I only have a week to figure this out.

Oh..and there is a pipe underneath my water tank that I use to drain. What would happen if I attached a water hose there instead?

Thanks for any advice or tips.