How do you keep your nipple watering system from freezing?

[BJnMe]

I want to use a nipple watering system, but it gets real cold up here in Michigan in the winter.

 

[jmagill]

I have my nipples in a bucket and I dropped a small aquarium heater in the bucket. Only did that this spring, so only tested to 15 degrees.

Worked like a charm.

 

[Organics North]

The same small aquarium heater. (Except I have a PVC pipe my nipples are mounted too.) My coop is well insulated so it never gets below 15 even when it is -30 outside. I put the heater on a thermo cube (on 35 off 45) so I do not need to think about it.
Works great.
ON