Gas conditioning tower is a equipment used to cool hot air in the cement industry. This tool has a water tank. The water in this tank will be sucked by the motor pump and then sprayed through some nozzle in the gas conditioning tower. The problem is the overflow of water that exceeds the tank capacity. This results in flooding in the area around the tank. There are several causes of the occurrence of the water flood. The first cause is the type of valve used previously not in accordance with the required specifications. The required specification of the valve should be able to close tightly. The previous valve is the lift check valve. This valve is not suitable as a closing valve. This valve should be used as a backflow prevention. The second cause is a float that can not manage to open the valve cover perfectly. The float used is the level control of the ball floater model. These floats tend to be unstable and lack the force to drive the lift check valve. the third cause is the use of automation system with mechanical working principle, where the monitoring of valve performance and water level can only be done directly from the tank. To set all the above systems to function in accordance with the target automatically, then Programmable Logic Controller (PLC) is used as the controller of this system. This study aims to design and implement a water tank filling system in the conditioning conditioning tower area automatically using PLC and analyzing problems that occur before implementation. It aims to reduce the cost of water use and facilitate the supervision of the Central Control Room. Study observations were conducted by taking into account various aspects such as the right type of valve and valve effectiveness testing. The results obtained from the use of lift check valve, from October to December declared 104 times with a total time of 441.8 hours. Meanwhile, after using the ball valve, from January to March no leak has occurred at all. The results obtained from the implementation of this automation system can reduce the cost of water use and the cost of chemicals used for water additives.