Re: Kevin's tank design.
>Way back when, Paul Krombholz wrote:
>> (picture deleted)
>> The pathway of the nutrient water flow above the tank water level will have
>> to be completely air tight. If air can get in, the weight of the water
>> column above the tank water line will force the nutrient solution up
>> through the fine mesh and through the gravel into the tank water.
>Am I missing something? My EE brain figures that because the water flow
>up the riser tube on the left is exactly matched by the flow down the
>tube at the right, there won't be any mixing between the plenum and
>the main tank water (to a first approximation). Water level in the
>aeration chamber (which must remain open for oxygenation) is set by
>the height of the outflow tube.
>Since, as Paul Sears mentioned, there will in fact be low pressure at
>the base of the left riser tube due to the powerhead, there might be
>some water sucked down from above, but the amount of mixing should be
>negligible at low flow rates.
>Kevin Conlin Montreal, Canada "We're Canadians. We HAVE to be polite"
It took me a long time to think about it, my brain not being an EE type,
but now I see how your thinking goes (I think!).
When you start up the power lift, the water will rise in the up tube and
drop in the down tube, indicating a lower pressure. Water will then flow
in through the gravel into the nutrient solution chamber until the level in
the down tube is back to a level which should be a bit higher than the
water level in the tank. The distance higher will be equal to the height
of the water in the aeration chamber. As long as the pump pumps at a
constant rate, the system should be in equilibrium, and there will be no
pressure differences between the nutrient chamber and the surrounding
water. If the pump should stop, then water would fall in the up tube and
rise in the down tube, and there would be positive pressure in the nutrient
chamber which would cause nutrient solution to be forced up through the
gravel until the levels in both tubes fall to the water level of the tank.
So, the system should work as planned as long as the pump pumps at a
Why not try a test run with the system with a dye in the water of the
nutrient chamber. You could then let the system run for several days and
see how much of the dye gets in the tank water.
Paul Krombholz Tougaloo College, Tougaloo, MS 39174