There are products at your local auto parts store such as Epoxy Ribbon, JB Weld, and others that don't require heating you can use to patch the leak. Be sure and follow the directions on the package.
You can't BEAT KENT'S ALL IN ONE.
on the fuel line running from the tank to the carb.
There will be an inline filter on the fuel supply line from the tank to the carburetor
believe it or not,I used a Turkey Baster to drain my tank to change a fuel filter.
fill tank, to top of neck, watch the leak area, [don,t start it]
from around the fuel cap or the fuel can you use to fuel it. if it is a metal fuel tank then you can get rust built up in it and it starts to flake off
Fuel tank cap vent is plugged.
it may not have one. If it does it will be located on the fuel line between the fuel tank and the carburetor.
To remove the gas tank on a 1998 6.75 hp self-propelled Craftsman lawn mower, first ensure the mower is turned off and cool. Disconnect the fuel line from the tank, being cautious to catch any spilled fuel. Next, remove any screws or bolts securing the tank to the mower's frame, and carefully lift the tank away from the mower. Make sure to handle any attached components gently to avoid damage.
add a fuel treatment to remove water if it is a small amount or drain the fuel and replace with fresh
it will probably explode or it will burst into flames either or its bad
If you tilt the mower to get at the blade for sharpening, or go down a particularily steep slope, gas will run from the tank out through the filter.
That will vary for each make and model of mower.