You can make these adjustments to the Gemini toilet and fix your leakage problems regardless of your level of toilet troubleshooting expertise.
Shut-Off Valve and Cistern Draining
Ensure the shut-off valve at the bottom rear of the Gemini toilet is properly adjusted. This valve must be turned off before you begin cistern troubleshooting. Use your hands to turn the valve all the way clockwise to shut off the flow of water. Pull down on the Gemini's flush handle once the valve has been turned off. Hold down on this handle until the cistern drains of water completely. This finishes the troubleshooting preparation.
Water Tube Coupling Adjustment
Examine the water tube on the left side of the toilet. About midway up the tube and just across from the base of the cistern is the water tube coupling. The tube attaches to this coupling and leakage commonly comes out from around the coupling if the tube is not properly adjusted. This leakage will cause water level problems in the cistern over time. Adjust the water coupling over the tube by twisting the coupling clockwise with an open-end wrench.
Flapper Valve Replacement
Pull the lid off the Gemini's cistern to access the flapper valve. The flapper valve is connected to a chain hanging from the handle. Remove the chain from its connection point on the flapper valve using your hands. Position the replacement flapper valve into place and attach the chain.
Final Adjustments
Put the Gemini's lid back over the cistern. Twist the water shut-off valve back in a counterclockwise direction to re-enable the flow of water to the Gemini toilet. Pull down on the flush handle. This will refill the toilet's cistern and resume normal operations. Leakage will no longer be an issue.