The flapper valve on my GE portable potscrubber 720 is leaking water extremely bad all over the floor what do I do to fix this issue.

SOURCE: Flapper valve

You will need to adjust the chain. They are just clipped at any point when coming from the factory not at the opyimal length. It will take a little effort to find the desired length as sometimes the trick to getting the valve to remain open longer is opposite of what one would expect. I mean there is a point to where there will be more slack in the line than you might expect to get the valve to stay open for the optimal duration.
Hope this helps you.

SOURCE: Toilet Refills Every 15-Minutes

I have minute amount of leakage into the bowl causing mold to grow. I believe that it may be the rubber seal for the flapper body to the porcelain.

SOURCE: water leaks from tank to bowl till water level in the tank is jus

Yes. You will have to remove your tank from the bowl to replace the defective fill stack(the tube thing your flapper is attached to) it is not as hard as it seems.First remove water supply tube.Then remove the through the tank bolts. should be two of them. Lift off and turn tank upside down. remove spud gasket. Unscrew old stack. You should be able to get a universal kit to work with your tank and should come with all new parts including new flapper and spud gasket. You will need new through the tank bolts and note the sequence of assembly to get water tight seal on tank. Hope this helps

SOURCE: I replaced my Sterling 1.6GPF with universal

make sure chains not too tight otherwise it holds the flapper open just enough to let water thru

SOURCE: water leaks into the bowl through flapper.

THE THING THAT THE FLAPPER SITS ON IS CALLED A DOUGLAS VALVE. EITHER SAND AROUND THE RIM OF THE VALVE WITH FINE SANDPAPER. UR TRYING TO REMOVE ANY IRREGULARITIES ON THE RIM OF THE VALVE. IF THAT FAILS TO SOLVE THE PROBLEM, TIME TO REPLACE THE VALVE.

Testimonial: "Thanks for the help. I did that but used very fine steel wool. No help. Called a plumber and he replaced everthing that could be replaced. "