This circuit was found in a 1966 General Electric documentation. It makes use of direct contact water sensors and therefore requires an isolation or low voltage relay drive transformer.
The operational amplifier taken as an example is uncommon today, but the configuration can be made...
The integrated circuit used in this regulator is not easy to obtain, since the publication is from...
This configuration was obtained in a 1977 FET Databook. The circuit can be practically any JFET...