Image Number 3 for United States Patent #4211249.
A liquid level control system is disclosed for use with a swimming pool or the like having a pool reservoir, a main drain or outlet, usually at the bottom of the reservoir, and an outlet located at a predetermined water maintenance level for the pool. The system includes fluid amplifier means positioned relative to the pool reservoir for sensing an interface between liquid and gas, or water and air, at the surface of the water in the pool and developing a fluid pressure signal when the interface falls below a predetermined level. Liquid circulation means, including a skimmer at the surface of the water in the pool reservoir is provided for circulating water from the pool reservoir between the outlet and an inlet. A portion of the water circulated by the circulation means is channeled to the fluid amplifier means for operating the same. Fluid valve means is provided which is responsive to the fluid pressure signal developed by the fluid amplifier means. The system further includes water supply means for adding water to the pool from an external supply thereof when the fluid valve means senses the fluid pressure signal developed by the fluid amplifier means.