LOL! You are more than welcome. Water is a funny thing. It can be pressurized, but not compressed. If you were to take the edge of your hand into a bucket of water, it would displace the water and you would not feel anything, other than your hand being wet. This is what I sometimes call soft water. Now if one were to do a belly flop from a diving board, your speed of decent is greater than the water can displace, thus you get that sharp sting on your tummy. This is hard water to me. If you have any pressure on the supply line, the line will reach equal pressure with the source and lie in wait as 'hard water.' A vented gravity setup is 'soft water,' it only has the force of the established head pressure, it can not be greater than this and as it is vented, it can not squirt, nor hold the stored pressure of being connected to a hose with a tap on, regardless of how much it is on.
Water will not compress, put enough force/pressure upon it and it will always burst the vessel. Always. So a closed system that could automate your setup could be had with a float valve from a kit or toilet. That way you could, if you wished have some automation in your desired water system. I know of some whom do this, I do not. I like to 'see' the birds and check the water on a regular basis, this helps keep me from being complacent in my chores. A word on vent holes, 1/16 of an inch is enough, I also have some that are a quarter inch. I like them small, in order to keep the dust out of the bucket as much as possible. There is no real magic hole size, just big enough so as to not get plugged up or somehow stopped up. Any thing larger than this is fine. Water under pressure will cut metal, as hard water, the same water in my glass during break time, quenches my thirst, as soft water.
If I have made a mess of the above, I'm sorry. It is easy and fun to mix and match the two types of water, to meet whatever need you have at hand.
Good luck with the project,
RJ
