My fish tank heaters have thermostats on them, but when I tried one in my container pond(40 gal) one winter, it burned out since it was working too hard.
Not a good application for an aquarium heater.
Work good in my setup, tho the cheap heater I bought at first failed.
Next one was a better one and has lasted 5 years so far.
https://www.backyardchickens.com/articles/aarts-heated-waterer-with-horizontal-nipples.67256/
Don't bother with pipes, or pumps.
Here's my thoughts on 'nipple training'.
First, it's good to know how much water your flock consumes 'normally', I top off water every morning and have marks on the waterers so I know about how much they drink.
Found they drank just as much from the nipples as they did from the open waterer.
-Do not train to nipples during extreme temps when dehydration is more of a risk.
-
Show them how with your finger(tho that might just train them to
wait for your finger),
and/or manually grab them and push their head/beak onto the trigger(easier with chicks than adults).
-
No other water source, best to 'train' during mild weather when dehydration is less of an immediate health risk. I do provide an open waterer late in day to make sure they don't go to roost dehydrated, especially young chicks.
It can take days or weeks to get them fully switched over, just takes observation, consistency, and patience.