I watched a video that uses gravity to boil water just by lifting it and lowering the pressure. explanation is better in this video
https://www.youtube.com/watch?v=hHNoHhbfFDQ
so I’m running the scenario through my head of lifting the bottle to the point of “cold” boil then lowering it down (while keeping the hose above boil level to avoid contamination from the original) and I’m trying to figure out what the issue would be.
would the water vapor never condense until a temperature change happened, would it be too slow at distilling since there can only be as much water vapor can only be as much as the container?
what are the flaws or limitations
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I’m writing only based on your text, not the video, please excuse any doubling of content.
It is easier explained if you build an imaginary machine instead of lifting / lowering that does the same thing. The single most important thing to understand is that the lower the pressure the less heat you need to add to boil something. There are funny graphs for each liquid (for example https://courses.lumenlearning.com/umes-cheminter/chapter/vapor-pressure-curves/ ).
The intro explanation
The water in your containers will behave based on their individual combination of pressure and temperature. I’d at any point the water vapor falls below its boiling point at the current pressure it starts to form a liquid. At this point you’ve made a fancy rain machine.
Note that water itself adds pressure to a system because of its volume even as a gas
A machine
Imagine you have a container at 100 mmHg which according to a random online calculator leads to a boiling temperature of 50 degrees C.
Now you heat this up and lead the water vapor into another chamber which has only s pressure of 10 mmHg. Water has a boiling temperature of only a bit over 10C there! So you keep it at 20C to be sure the water never gets liquid again.
But wait: now you’re adding water vapor into a low pressure container - you’re literally pressing a gas into it - so you increase the pressure in there.
The first container, the source of the gas, becomes irrelevant: As soon as the additional water increases the pressure to around 20mmHg it starts condensation again as now it’s boiling point moved above the 20 degrees.
The flaws
As you’ve asked for the downsides: it’s a very convoluted way of manipulating water to achieve the same result as simply heating it. You would need way more energy to lift the containers far enough or otherwise decrease the pressure than the energy needed to boil it.
Other than energy and logistics I don’t see a downside. Liquids don’t behave differently in terms of boiling no matter the source: pressure, temperature or a combination.
You could lower the bucket to boil the seal container.
I do have trouble imagining two containers with two different pressures but I get you can have a pressure valve like in a refrigeration system.
The pressure on the seal container would seem to be the same pressure as the phase changes. The container in the video was crushed by the atmosphere so that implies the pressure is lower than atmosphere post phase change.
But there seems be an issue once the water has became vapor like would the boiling point move enough so that the water would condensate and would condensation reduce the pressure thus lowering the pressure and boiling point.
There would be water in both the containers and tube. Seems strange that water in the tube at the vapor/liquid barrier would evaporator then condense in what’s essential a similar environment. Its possible when I think about it just the seal container water can evaporate and go back into the tube
I can’t really do calculations because I don’t know the process yet, but I think boiling water would be more energy than lifting water 34 feet since water heat capacity is so high.
Right now I do think the flaw would be it being a slow process or even inefficient
Raising it lowering the container works only if it is not protected from environmental pressure - but you’re right: creating two different pressure environments that are somehow connected is ready in a thought experiment but then you tell that to the engineer and they get their third heart attack of the week…
Depending on the purpose of the distilling, heating to a lower temperature might not kill pathogens.