Water Wicking between two containers

[cultural_piccolo_836]

TL;DR

Creating a self watering window sill set up. Want my make shift water butt to top up my main plant watering source via wicking/ capillary action. Water butt is on the ground and is 15L and the water source for my plants on my window sill is 12L. Why is it not working?

I am trying to create a reasonably self sustainable watering system for the plants on my work window sill. Currently I have a 12L bottle (half empty) which (via wicking/capillary action) is watering x2 tomato plants, x1 courgette plant, x1 sweet pepper plant, and it is all going very well. Obviously after getting this to work well, I have now considered myself a person of science and have sought to expand my new found skill set.

Alas, this does not seem to be going the way I imagined. The bright idea was to create a make shift water butt on the ground which has a greater volume than my window sill water source so that it could top up my window sill with zero effort....this does not appear to be working. I'm trying to establish if it is as a result of the following reasons:
1. Even though the volume of the ground based water butt is greater that window sill water source, gravity is ruining it and the water butt needs to be higher than the source it is feeding.
2. Even though there are 4 plants slowly pulling water through capillary action, this is not enough movement to pull water through from the ground source.
3. The water butt needs to have a X amount increase of volume to feed the window sill.
4. I need more than x1 wicking thread between the two water sources.
5. This is not how science works.
6. Other.

 

[Baluncore]

Welcome to PF.

You are fighting an uphill battle.
If the wick at the top is in the water, water will flow from the high to the low reservoir.
If the wick is above the water at the top, it will NOT drip into the upper reservoir, as the tension needed to get the water up there will prevent it dripping into the higher reservoir.

Avoid the use of an upper reservoir. Consider using a wick material with a much finer capillary that will provide more tension. Then make sure the plants have their roots in the top of the wick. Run the wick through a tube to reduce the loss to evaporation.

 

[sophiecentaur]

Avoid the use of an upper reservoir.

This is the clincher. An upper reservoir will just empty itself through the wick without any regulation to keep the bottom end at just the right height. The only system I could imagine would involve some electrical servo system. If that were really practical, I'd have thought it would already be sold for people who love their indoor plants enough. Problem is that it would probably not be fail-safe . . . . . .

There are systems (electrical) which turn a valve on at a regular rate and they do sort of work. I had one in a conservatory but it was no substitute for a daily visit from a human because there was no feedback to control the net flow. The same sort of thing is fine in a garden which can literally soak up any errors.