Two Flow Sensors wired to One Sensors Slot

I have two separate main lines running to two separate valve boxes and will therefore require two flow sensors to monitor the overall flow of water. I also have a rain/freeze sensor installed, so I cannot wire the two flow sensors to separate sensor slots. Can I connect the two flow sensors to the same sensor slot on the Gen 2 Rachio controller?

I know there may be a slight increase in the inaccuracy of the flow sensors reading since one sensor’s last “click” and the second sensor’s first “click” will not line up on an even measurement boundary. The wires to the two sensors are shielded twisted-pairs, and should have minimal interference. Since only one valve will be running at a time, only one sensor should be sending “clicks” at one time.

I cannot see any logical reason why this would not work except for a possible power issue. From reading other posts, I don’t think this would be an issue since I don’t have a master valve or a pump that would be drawing additional power. Is there anything that I may be missing? Thanks.

What model flow sensors do you have?

Many flow sensors which are not actively powered (do not need to be connected to SC and SP terminals) will use mechanical actuators and generate the signal by shoring the output during a particular angular position(s) of their internal rotor wheel. These sensors tend to have a wide operating voltage range and AC/DC voltage compatibility.

What this means is that if one of the flow sensors has stopped in the “shorted” position, the output will remain shorted until more water will flow through that sensor. The problem is that if one of the flow sensors is shorting the output, the other one will essentially be “dead” and Rachio will get no readings from it.

I’ll think about your problem some more, but meanwhile let us know the model number of your flow sensors and we’ll go from there.


Luckily, I have not purchased them yet, but was highly considering the CST FSI-T10 1 IN Flow Sensor. If that one wouldn’t work, which flow sensor would be better?

Actually it is one of the sensors supported by Rachio: Full list is here (link)

It also says that it uses an output pulse of 5 ms, meaning it has active electronics and will not keep your signal line tied up.

It doesn’t look like having two of them connected in parallel would cause any issue(s) I can think of.

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