Automatically drain when cold?

I’ve got a subsurface drip irrigation system and I don’t have to worry about freezing the drip lines, but I think I froze my backflow preventer - which leads me to start to think about how to be able to “set and forget” my system to drain.

My current idea is to add a master valve to turn off the supply to all zones, using the Rachio to automatically open the valve. That can be used 100% of the time.

But I’d also like to have the system automatically drain the supply line when the temp drops below 32 outside.

Is there a simple way to have the Rachio do that for me? All I’d need to do is have another valve which stays closed except for 5 minutes or so when it’s freezing outside to allow the supply lines to drain.

Ideas about how to do that?

Master valve is always a good idea with any irrigation system. Do you have an isolation valve to your irrigation system? Normally its installed in the easement close to the water meter. I dont know of any way to drain your lines from the controller. Do you have King Drains on your lateral lines. As far as the backflow, go to youtube and look for backflow winterization.

Yes I have a master valve that controls the flow to all zones and isolates the irrigation system from the home water source.
Yes, I have drain valves for each zone.
Yes, I understand how to manually winterize the system.

My question is about how to use the controller to open a drain valve automatically when the temp drops below freezing.

Pretty easy to do if you have a spare zone on the controller. Simply wire the drain valve to it and don’t include that zone in any schedules. Connect rachio to ifttt and create an applet that triggers when the temperature falls below 35f and have it run your drain zone for a few minutes. Don’t use 32f as it may be too late by then. Also you’ll want a way to disable your schedules AFTER that for a freeze delay. You can use ifttt for that also and set it at 32f as the freeze delay maybe disable the drain command. I doubt it though. Freeze delay likely delays schedules only so maybe after doesn’t matter.


The more I think about it, you want a freeze delay first to disable the schedules. Imagine it drops to 35f while a water cycle is running.

I’ve not observed how a valve operates under low pressure conditions. It’s possible the diaphram spring will retain water in the system. It’s possible the valve will not open or operate without water pressure as they are siphon/pressure operated.

Good thought. I was wondering about ifttt support.
I’ve got some spare zones on my controller.

I’ll take a look at that. Thanks.

@Tomcooper If you want to truly winterize your backflow preventer, you will have to take it apart. The device will hold water in the check valve chambers. Then, you should have the backflow device retested to make sure it’s working properly after rebuilding.

I like your idea of draining though. The other thing to think about is refilling the mainline when it’s empty. If you turn on the master valve to fill the system at full pressure on an empty mainline, you could have all kinds of water hammer damage to joints.

Here is a video that explains how a King Drain works. It is impossible to wire these valves. Here is a youtube video that explains how they work automatically:

So if you have a master valve, isn’t it automatically open whenever you’re running any zones? I can’t see any way at all to run a zone that’s actually a drain without having the master open and therefore running water out of the drain the whole time it’s open. Am I missing something?

Yes I think that would be an issue. It would require a separate system to drain. Those King valves might be a better solution.

I’ve been pondering the freeze issue myself. Not for an irrigation system but for my cabin that often sees freezing temps. Draining the lines is often an involved process not really knowing if things are going to freeze in between visits and whether to drain water heaters also. I have temperature controlled outlets for line heaters as well.

OK, found a solution that takes a little work, but is cheap. I’m still waiting on one of the parts, so I’ll update to confirm that it works and post a circuit diagram.

I was interested in running two drains, which means two zones that need to run when the low temp threshold is reached, at the same time as the master is closed. The solution is to use a relay to close the master valve whenever the controller opens it when the zones connected to the drain valves are run.

While the Rachio is itself 24v DC, what I didn’t realize is that the common valves are 24V AC. For this reason, my initial solution to use the power wire from the drain zone to turn off the master didn’t work; 24 V AC didn’t flip my 24v DC relay (of course). I only thought to check out what the power requirements were for the valves after I figured out that my relay was never closing.The solution to that is to use a bridge rectifier to convert the AC to DC, so that the relay works. The relay is actually two in one, which lets you shut down the master if either of the two inputs is high, and will take the 12v output of the rectifier with a jumper setting.

Here are the parts I’m using:

AC-DC Converter 6/12/24V to 12V Full-bridge Rectifier Filter Power Supply Module

DC 24V 2-Channel Relay Moudle High/Low level Trigger

Another challenge of course is that the Rachio on IFTTT doesn’t let you start and stop individual zones or even a routine, so more challenges…

I’m excited about the possibilities. Of course, it was 90 here yesterday, so freeze is a ways off. :wink:

I just looked at IFTTT for Rachio, and it looks like I can start a zone based on weather?

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