A little side project one weekend turned into a novel idea! The wife left the sprinkler on all day for our garden by mistake so she asked me to automate it. We already have the following hardware...

The only thing missing was a rain sensor like the Orbit Wireless Rain and Freeze Sensor for Sprinkler Systems which we have used in the past. Then it hit me! There are shortcomings of these hard-wired rain sensors (besides the investment)...

  • Mounted to the house they won't be accurate from all directions
  • No output of dryness level (only a water or don't water switch)
  • No input of sprinkler water received (unless you mount it where it gets hit)
  • They will allow the sprinkler to run even during rainfall
  • No input of weather forecast data (percentage) or per-storm rainfall totals
  • Decent brand with freeze sensor and adjustable soil permeability is over $30

A personal weather station like the Vantage Pro2 Plus can cost hundreds of dollars but would give us the accuracy we are looking for.

So I set out to create a "virtual rain sensor" which happens to be the original name for the site. It evolved into much more than that - a hosted solution that gathers information from personal weather stations for the past number of days (configurable interval and weather location). It then runs a variation of the Penman-Monteith algorithm to calculate losses through transpiration and evaporation based on sunlight, wind, temperature, relative humidity, barometric pressure, elevation, and regional reference surfaces. We then apply the gains through rainfall from mother nature. It also pulls the forecast for the next day and the average per-storm rainfall total for the current day and calculates a predicted rainfall total for the next day.

Taking all this into consideration (and whether the current observation or forecast low is at or below freezing) we calculate the duration of our watering based on our inches per hour calibration (using a coffee can in your garden you run the sprinklers for an hour and then measure how many inches of water you collected). We turn each X10 zone on for the calculated duration and then we turn it off again.

The results are in...

Switching from a timer-based system equipped with a rain sensor will save you about 42%
Switching from a timer-based system alone will save you about 72%

Savings are based on water consumption for irrigation application, not your household water bill!

Take complete control of your irrigation from anywhere in the world and get the accounting, ordinance compliance, and water savings you expect!

The application runs as a service on any Windows operating system (XP or 2003 Server minimum). Based on each zone's configured interval it will download a small packet of weather data from our servers and make a decision. The details of this decision will be recorded and viewable on your dashboard.

This is still a "beta" program so there are undoubtedly bugs. I have set up the dashboard so you can monitor and configure most aspects of the operation. Participants in the "beta" will retain their accounts for an indefinite period free-of-charge.

Please report any problems and feel free to make suggestions or requests here or check the status of an existing issue here. Thanks!