Low Water Pressure Cutoff

I have a Munro Pump Smart Box on my irrigation system that cuts off the pump if there isn’t irrigation water available. Currently this event isn’t noticed by Rachio and it continues thinking and presenting that the sprinklers are happily watering away even though they aren’t. How do I properly integrate the Smart Box status so I can get a notification that the sprinkler system has stopped?


@grandvalleydave - Here is my guess. Based on this instruction sheet -> http://www.munrocompanies.com/MunroCompanies/media/Resources/Smartbox-Manual_1.pdf I’d put a SPST NC 24VAC (Single Pole Single Throw Normally Closed 24 V AC coil) relay in. I’d connect the SC (Sensor Common) port from the Rachio to one of the poles on the relay and the run the wire from the other side of the relay pole to the S1 port on the Rachio. Then I’d hook the wires on the relay coil up to terminal 6 and terminal 2 on the time delay relay in the Smart Box. Don’t forget to enable S1 as a rain sensor in the Rachio application.

Here’s the why. It appears the Smart Box time delay relay is powered from the Rachio Master Pump circuit. The Master Pump circuit is only energized when a zone should be watered. As the rain sensor circuit is a normally closed circuit, we need current (power) through that circuit when there is no watering - this is where the relay comes in. When the pump isn’t running the pressure will be below the threshold so we can’t run the relay off the pressure switch circuit as it would always be below the pressure setting when the pump isn’t running and therefore it would never water. It appears the time delay relay in the Smart Box gives the pump a little time to build up enough pressure to close the pressure switch before activating. If the time delay relay in the Smart Box triggers, I believe terminal 6 would have power and terminal 2 is the common, this would trigger the SPST NC relay to open the circuit which would tell the Rachio “it’s raining”.

Hope this helps and “your mileage may vary”.


Thank you for the reply and the suggestion! I will give it a try.



@grandvalleydave -Let me know how it works or if you need an example relay as I found one that worked for a different issue.

There may be a way to use the time delay device in the SmartBox, but I couldn’t find what all the connectors on it were for. This would be the safest and surest way.

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@grandvalleydave, I’ve never used one of these but have heard good things about them. Sounds like you’re probably using this model?

Another question to consider is if the well refills and the controller is still “running” a zone, I’d guess the pump would kick on again, allowing you to continue watering? If so, enabling a rain delay would cancel out any future watering on that schedule…

Actually, the box I have is this one.

There is no well. It pull directly from an irrigation canal (piped) and since the neighborhood system is quite complex and old, there are frequently times when there isn’t enough water in the line to run the sprinklers, so the Smart Box cuts power to the pump to avoid burnout.

There is no auto-restart if pressure returns. So the rain delay approach previously suggested would seem to work well. At least it would notify me when the system stopped pumping so I could manually run the system later when there was water. Otherwise Rachio thinks it is watering, I think it is watering, but it isn’t and that is no good on any front.