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New Member


Friday, June 22nd 2012, 1:27pm

Controller help

My in-laws recently bought a "winter" home near us in Tucson, AZ. The place only has two irrigation valves. One goes to two citrus trees that are on bubblers and the other goes to a drip system that hits all the shrubs and other plants in the yard. No grass involved here. The current timers are electro mechanical with the dials and pins that you either insert for the length of time you want the valves turned on or remove for the days you want to water. One timer for each valve.

I can't divide the 14 day watering day wheel up evenly, so have errored on the side of watering too often rather than going too long. So, I'm looking for advice on a better timer. I stop in at this place currently about once a week just to make sure things are still alive. Would the Rainbird ESP-SMT be a good solution for a house that's not lived in but 4 months a year?



Friday, June 22nd 2012, 1:40pm

It's a great controller but far more than you need.
It's a SMART controller, needs detailed programming and will adapt to weather changes.
However, for your 2 zone system look at either the Rain Bird SST or K-Rain RPSif you can use an indoor timer.
For outdoor, look at Rain Bird ESP-4M or the K-Rain 3604

Save you a good bit of money.


New Member


Friday, June 22nd 2012, 3:20pm

Thanks for the reply. It is an indoor install - should have mentioned that.

We currently are in our severe weather season here where it's extremely hot and dry, but rain is hopefully just around the corner. And hopefully it will come down in buckets! A controller that could adjust itself to account for rain would save me some trips over there to constantly adjust it. It looks like the RainBird model you referenced will accept the input from an optional rain sensor. Looks like this one would probably work.

So the operation of that would be once the sensor sees a pre-determined amount of rain, it shuts the controller off for up to 72 hours? That would be great as that's really all I'm looking for. Let's say it gets 45 hours into that 72 hour delay and it rains again. Does that then reset to another 72 hours?



Friday, June 22nd 2012, 3:44pm

Don't give the rain sensor credit for being smarter than it is. It's pretty dumb.
Basically it is a stack of felt washers. As it rains they absorb water and swell. When they swell to a certain point they press against a switch and break the circuit.

When the rain stops they start drying out according to humidity and sunlight.
Overcast and cool could mean days. Dry and 100 degrees blasting sun could be next day.
In theory it is similar to the rate your soil dries.

Remember that a sensor cuts off after a certain amount of water, not as soon as it rains.
Say you get a good rain, sensor fills, swells, cuts off switch.
A day goes by, sensor dries out 30%. Then it starts raining.
Sensor will not break circuit until that 30% is refilled. Then it cuts off controller and the cycle starts again.

They are easy to test. Install, start system, push button on top, system stops.
Really curious? Pour glass of water over it slowly (have to give felt time to absorb moisture and swell). System will stop.

They do work pretty well. Low maintenance, easy to install, etc.
And they will save you some driving.


New Member


Friday, June 22nd 2012, 5:29pm

Thanks for clearing that up. I was reading in the manual for that SST controller where it talks about how to set the rain delay duration using the "Rain Delay" button and assumed the rain sensor would function the same as if I pushed the Rain Delay button. I see now that is not the case. I agree too though that it should still function in a useful way and save some water.



New Member


Friday, June 22nd 2012, 6:54pm

I started thinking more about that rain sensor and thought of something else. It sounds like it works by interrupting the signal from the controller to the valves and doesn't change any settings on the controller itself. I currently have the citrus tree zone coming on once every five days or so. If it rains on the day the trees are supposed to water, they will miss out and not get water (assuming no more rain falls) until another five days has passed, right? And that little bit of rain won't be enough for the trees.

Could I put the rain sensor in series electrically with the other valve (drip zone) instead? That zone is currently on every other day and would benefit from (and survive!) a rain delay.



Monday, June 25th 2012, 8:21am

One thing I really like about this job is the incredibly imaginative solutions that come up for different situations.

DISCLAIMER: Not an approved design, factory won't back you up, may cause end of world, wake up vampires, etc.
I guarantee Sprinkler Warehouse won't back this up. I know because sales would ask me and I'd say no.

All that said I don't see why it wouldn't work. Install between control line (not common) and solenoid, it gets wet, circuit breaks, no spray. Worst case is you are out $20 and labor/time. I'd really like to see the results.

How much rain does the citrus zone need? If you set the sensor for 3/4" and it gets that on a water day, would that not be enough until the next water day?


New Member


Monday, June 25th 2012, 11:28am

Glad I am able to provoke some "outside of the box" thinking!

The citrus needs to be watered to a depth of 24-36" infrequently. They are in an earthen bowl and on flood irrigation. It takes 4" of water in the bowl to penetrate to that depth in our soil. We only get 12" of rain here a year in a good year, so they need much more than that to survive. And the rain sensor could really hurt these trees if they were to miss a watering this time of the year.

The other shrubs and smaller plants on the drip line would be very happy with small amounts of rain though. Using the rain sensor on that valve alone would definitely be useful. I'll see what my father in law wants to do and let you know.


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