Water Level Controller

This page is a work in progress while we continue development.


This is a simple controller for basic water level control or with timing enabled for hydroponics systems such as flood-and-drain.

Water level control:

Using the 5 probe sensors there are two methods of water level control, or maintaining a water level:

  1. Using 2 probes and maintaining the level between them; fill-on at the lower probe and fill-off at the upper probe. This allows the level to move over a wider range – run the tank down and then fill it up.
  2. Using 1 probe to maintain the level at that point; fill-on when the probe is dry and fill-off at the probe is wet. To reduce cycling and oscillations, short time delays should be included.

Water level control is the simplest function, used to maintain water levels in tanks, troughs etc. The controller can operate a pump or solenoid-valve.

Water level control can also be used to pump water out, as with a sump pump.


The controller runs a pump that floods the grow beds. When the level reaches the top the pump stops and the grow beds siphon back. A time delay and then the cycle repeats.

Sensor Probe:

This consists of a small circuit module and up to 5 (or 6) sensors. There is one common wire the full length of the sensor and a probe wire for each of the and each sensor probe. The probe passes a very small current through the water between the common wire and the individual probe wires.

Construction of the sensor probe is up to you and will depend on the situation, water quality, life expectancy, maintenance, etc.

The probe area in contact with the water must be large enough to “make a good contact” to ensure reliable detection.

The test probe consists of a set of 1mm diameter stainless wires of different lengths insulated using with heat-shrink tubing leaving only a 5mm tip exposed. The common wire is exposed over its length.


The controller can be supplied as just a circuit board or as a enclosed controller.

ELECTRICAL SAFETY – The board and relays are rated to switch mains voltages up to 240VAC. Appropriate mounting and safety must be considered if using the circuit board rather than the enclosed controller.


LED and Push-Button:

The LED indicates various states:

  1. a strobe flash every 2 seconds = normal, no flow
  2. slow flashing = normal, flowing
  3. fast flashing = alarm state, no flow, requires reset

The push button has several functions:

  1. reset = clears alarm state
  2. stop = stops flow (note: flow may re-start depending on current mode and water level)