If you are having what you believe to be tank issues, just do a pressure test.
- Remove tank and empty all fuel.
- Place new/unused fuel line on the pressure (lid) nipple.
- Plug the outlet with something (your finger works nicely).
- Submerge the tank completely in a bucket of water, leaving the fuel line out.
- Blow fairly hard into the fuel line and see if any bubbles are escaping the tank. If it is from the lid a new seal may be all you need. Elsewhere then you will probably need to replace the tank.
- If tank is still good, make sure to remove all water and run some fuel through the tank to flush it just in case some water managed to sneak in.