The sump level monitor was built to work with an Ecobee RSM-01 input board I have in my daughter's home or my Home Monitor project. I added a relay to allow it to stand alone. I wanted something I felt would be more reliable and easier to install than an ultrasonic sensor. To this end, I started looking into pressure sensors and finally came across Freescale MPXV5010DP. It has a 0-5vdc output for 0-10kPa, which would be about 1020mm of water head.
Since I wanted local indication, I chose an OLED module to use in the design. Cheap, bright and this one had a two color screen. To provide interface, I added a relay for a dry contact output. I added a DAC (digital to analog converter) for a 0-5vdc output with more power than the MPXV5010DP sensor, this will also protect the sensor from possible wiring damage. Since I am using I2C communication, all is need is software changes to supply data to another Arduino.
I designed and had built a custom board for ease of connections. It provides enough flexibility for different configurations.
The sensor is connected by tygon tubing to a copper pipe that gets routed down into the sump. This allows for some discretion as to where to mount the monitor and keeps it away from the water itself..