I would like to set up a reservoir that holds water, there is only one exit pipe to the reservoir that leads to a container. I want the water in the reservoir to leave it and go into the container naturally and stop until a certain level is reached. No pumps or valves are to be used. When water is removed from the container, water from the reservoir will refill it.
I have tried four different set ups to try to achieve this and only one worked. I would love to understand why they failed. I will provide my understanding for each case. The basis for this experiment was the bird water feeders that allow water up to a certain level. An image of this can be seen in here:
(Please remember that the yellow container only has one exit through the pipe and is sealed off with a rubber seal.)
For my first experiment I used a cuboid container but instead of the hole it is replaced with a PVC pipe that leads to a container. When I carried out the experiment the container filled up to just above the pipe and stopped. A diagram:
(With the yellow being the reservoir, the black is the PVC, the green is the container and the blue is the water.)
This is my explanation for this working: When the apparatus are set up the water begins to fall out of the reservoir and into the container, with air entering the same pipe to fill the space the water left. It happens until the water rises to the top of the pipe, preventing any way for water to enter creating a vacuum in the reservoir thus water stops flowing. (correct me if I'm wrong)
For my second experiment I simply rotated the reservoir 90 degrees, and placed an elbow connector to the container
However, the water never stopped, it kept running after it passed the top of the pipe and overflowed. My original explanation for this is that this is a case of communicating vessels. Just that one of the vessels isn't tall enough so the water couldn't reach the same level in both containers. However, communicative vessels are both open to atmospheric pressure, when in this case one of them are not, therefore I cannot see why it still flowed as the opening was clearly covered with water with no where for air to enter yet water still poured. I would love an explanation for this.
Now for my third experiment:
The reservoir was held directly over the container with the pipe sticking into some of the water. The water poured and overflowed the container. This was not expected because when you do something similar with a water bottle or glass cup the water remains inside of the container without falling. Is it because of the pipe? Is the area of the exit a factor? I would think that it be an extension of the body of reservoir and not have an effect but yet it did. This I would love an explanation for.
Finally, my fourth and final experiment.
As you can see the reservoir has been rotated 90 degrees with the exit going into the collection container. Here the water overflowed as well. Even after water completely covered the exit hole it still flowed. I realised that if you rotate the elbow at the exit upwards the water will stop flowing and remain in the pipe, I believe this to be a similar case to experiment 1 just the collection container has become the elbow in the pipe. What concerns me is how is it possible for air to pass through the water and into the container when it was pointed downwards?
If this post was too long I apologise but I really need more information on these and why it happened the way it did. If i can be provided with the name of the physical phenomenon that allows for experiment 1 to work I will be greatly thankful because I have been searching for it for days and this was my last resort.