Flush valve toilets are different from standard tank toilets that are based on use running water to wash the container instead of water is released from a tankless toilet on the back. Changing a toilet flush valve for a standard tank unit requires converting the valve inlet to a line of standard tank and place the new toilet on the output with a new ring of wax. Once installed, the toilet tank will operate like any other unit, but will use the entrance of the ancient wall to the water supply.
Turn the water shutoff valve on the main water line 90 degrees clockwise to close the water flow through the house while you work. Place an adjustable wrench on the nut to the left of the tap in the tankless toilet flush valve. Turn the nut counterclockwise to loosen the nut pitch control.
Wrap the stopcock in a towel to prevent damage and the key places around the pitch control. Place a new wax ring on the flange. Wrap the threads of exposed pipes in the supply line where the tankless toilet flush valve is installed with pipe tape. This will lubricate and seal the threads. Place the new tank on toilet wax ring and press firmly in place.