Water Bowl

Check out this video to see the water bowl in action...

The water bowl is a stainless steel dog bowl with a section of PVC cut to fit on top holding the float switch.  The bowl has holes drilled in the edge aligning with holes in the PVC.  Zip ties hold the PVC in place.

The float switch drops when the water level drops and signals to the Arduino that a top-off is needed.

💡Lesson Learned: I ended dropping the float switch and just overflowing the water on a set schedule.  This float idea originally came from what I do with my aquarium water to keep it topped off from natural evaporation.  In this case, it makes much more sense to overflow the bowl to get some of the dirt out and really flush it out with the extra water just going into the yard.   Doing this at set times throughout the day works well.

The Arduino then supplies 24V to the sprinkler system solenoid to allow water to flow to the bowl from the sprinkler piping.

There is also a bowl inside the coop so the chickens have some water at night.  This bowl doesn't have a float switch, but since it's much smaller it fills up when the outside bowl is filled up.  There is an aquarium bulkhead in the middle of the bowl with a pipe going through the floor to the ground so any overflow goes outside of the coop instead of on the coop floor.

💡Lesson Learned: I cannot say I ever saw my chickens using this bowl.  I believe it is because my coop is pretty small and they only use it for sleeping.  In a larger coop, this makes more sense, but there is something about locking the chickens in without any water that just doesn't seem right.  I know I like a drink of water in the middle of the night.

The Arduino also flushes the bowl daily even if the float does not drop.

Very young Henny and Penny getting a drink!

Components

Stainless Steel Float Switch

I recommend buying a good quality, waterproof float switch, or per the lesson learned above skipping this altogether!  I had an experience in the past where a cheap float started to short out, and it's not worth the trouble.  Spend a few extra bucks and get a good switch.  Search eBay for "stainless float".  This may return results for just part of a float switch, like only the float element itself, so make sure you get one that's completely assembled with wires and waterproof sealant at the top.

Sprinkler System Solenoid Valve

This will vary depending on your sprinkler/home piping, but I used Rain Bird JTV075-ASV 3/4-Inch Jar Top Anti-Siphon Valve.