How much water are you putting in the bottle? You should NOT fill the bottom chamber past the “maximum water level” line. If the bottom part is full, you should not add more water since the white divider ring between the top and bottom chamber is not water-tight. If the bottle is filled to the proper level and you are still experiencing a leak, try to put your arm around the bottle on the bottom half and carefully lift it off of the cooler. Place your other hand under the float valve and push it gently up towards the bottle, closing the opening on the float valve. Is the float valve leaking? If it is, please contact us for a replacement. If you continue to experience leaking contact the Water Cooler/Dispenser Manufacturer.