[jennyJ]

I have a 94 4000 express just wondering how you determined the tank was definitely leaking.

First it was the odor.  The back bedroom would get a foul smell after each flush.  I didn't think anything of it - its a boat afterall...Then there were traces of black water in the bilge after a long weekend.  The well which contained the tank began to overflow in the bilge.  So to confirm, I pumped the tank, filled it with water via the overboard discharge.  I could clearly see that the water was overflowing OUTSIDE of the tank.