I often wonder if old toilet guts could do the trick? It has a float with on/off switch but would want some modifications. If they haven't used chemicals in the back tank, you could probably use used toilet guts.
I used to have a purpose-purchased livestock waterer like that.
I love the idea of using an old sink, a good rubber/plastic/whatever plug and a float valve.
Amazon doesn't want me to see the picture/item, so I'll just assume it's a standard float valve.
If you look at the commercial versions for use with livestock, there's a protective plate that keeps the critters from messing with the valve itself, and some of the fancier versions have the float completely hidden. I used to be confused as to why, but then I dealt with chickens and goats and got my answers. If you can figure a way to keep the float part out of the livestock's reach, and keep some sort of filter thing from allowing assorted floating bits from blocking the shut-off part of the valve, you'd have a winner!
I really like the idea of using old toilet parts and finding a good cheap stopper.
Once you find something that works well for you, please share the finished idea. I would be very interested in making such a thing myself.
Any stopper that fits the drain would work and the idea of being able to clean out All The Mud and plant bits and random whatever that poultry seems to enjoy dropping into water containers would be a blessing.
Thank you for sharing this lovely idea! It would make a lot of my watering problems go away. It would introduce some new ones, but at least the old problems would be gone! ;)
There is nothing so bad that politics cannot make it worse. - Thomas Sowell
Everything that is really great and inspiring is created by the individual who can labor in freedom. - Albert Einstein