Large Project

I have a hunter icc and have about 36 stations. I saw that I may have to get isolators additional to the rachio. Can someone confirm and if so, it would be 3 rachios, 2 16 zone and an 8 zone, how would this work? Can’t I use some kind of relay system if this is necessary? This is also an outdoor system so it would all need to be in the outdoor enclosures.

Here is the system in question.

Good news is that your setup does not feature a master valve or any kind of sensor that I can see, thus you will not have to deal with an isolator or any sort of relay setup.

I see that you have at least four common lines. It is possible that you will be able to segregate your setup into four separate groups, but you will end up bridging at least one group between two different Rachios. This should not be a problem since voltage potential needs two points of contact for current to flow, and having only commons interconnected between the Rachios will not cause an issue.

If you are considering Gen 3 controllers with their flow meter capabilities. @jsore has outlined (link) a way to make this work with three additional master valves, since each of the new master valves would be connected to an individual Rachio, there should not be a need for isolators.

Have you considered how you wish to setup your schedule? Are there any watering restrictions where you live?



I figured I would schedule the 2 large controllers to every other day and the 8 controller off hours. There aren’t watering restrictions but water is expensive here. Can you clarify the bridging between two rachios and if I need to do something different since they will be in outdoor enclosures?

Thank you for the help!


By bridging, I was referring to connecting the common wire together. Connection would take a form of a Y whereas there is a cable running from a common terminal of 2 individual controllers.

Something like this:


Connection can be done outside of the enclosure, if needed.

Rachio supports setting schedule to start or complete relative to a certain time. So if you set one controller to start on that time and the other to complete by the same time, they would work well gother. The third controller would need to be offset by a couple of hours to avoid multiple zones running at the same time.



I am wiring my system right now. Must the bridge be done to two separate units or can I bridge the 2 commons on a 16 unit?

all of the C terminals on the individual controllers are already connected internally, this is true for both 8 and 16 port versions. No external bridge is required, unless you are connecting two separate controllers.


Why would I need a bridge then if I can connect one common to one unit each and 2 to another unit?

You don’t if you can avoid it, but on the original photo you’ve shared, I’ve seen only 4 commons for the three controllers you wish to use. A zone will not work if the relevant common is not connected to the controller which is driving that zone.

Can you verify how many white common lines your system has?

Update. There were 4 common wires. So I bridged two of the rachios but I am running into some issues. The way the previous unit was wired was that there were 4 bunches of cables but different wires from the different bunches went to the different connector groups. I installed it the way it was on the connector groups but some stations aren’t working. I suspect the commons were all connected on the hunter but I am unsure. Would bridging all the commons be okay?

Yes, as long as only one cable is shared between controllers, everything should work fine.

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Could you clarify what one cable you are referring to?

Referring to my earlier drawing, if you connect one of the common terminals from Rachio A to another common terminal on Rachio B using one cable, the two are now bridged. If you proceed to connect another common terminal on Rachio B to a free common terminal on Rachio C, all three of your controllers will now be bridged, with Rachio B acting as a pass-through between Rachio A and Rachio C. You do not need to connect Rachio A to Rachio C as it would create a loop and introduce interference into the system. Note that you only used one cable to connect any two of your controllers.

Between the three of your controllers, you should have 10 common terminals. You would need four of them to bridge your controllers as described above, leaving you with six available terminals to connect your field commons. Where you make these field connections (which of the 6 available terminals you use), does not matter.

Alternately you can simply bundle all of the commons together (four from the field and one common from each of your three controllers, for the total of 7 wires) and connect them all with one wire nut. In this case you should only use one common connection from each of your controllers, leaving 7 common terminals left unused, which is OK for this configuration.

Remember to only connect / bridge commons together, if you try to drive one of the zones with more than one controller (thereby making a second point of contact between individual controllers), you would potentially create a circuit and damage your controllers.

You can share commons, but sharing zones / valves / power is a recipe for trouble.

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