I’ve been researching chillers for a little bit now. I do like the idea of not running nute solution directly through the chiller, and instead running a closed loop system with something like a wort chiller in the res. (just a winding of stainless steel piping, about the size of a bucket).
The question that I can’t find an answer to though, is how a closed system like that is filled. Any unpressurized closed systems I’m familiar with, has some kind of reservoir to keep the lines full without any air in them. An automotive radiator type system would work, but I don’t want to use copper.
I could just use another bucket inline, but there must be something more elegant that somebody else has already engineered, so any tips?
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Have you searched the aquarium guys doing diy chillers.
I’m digging the closed loop idea 
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A closed loop system will require some type of expansion device. This will accommodate the expansion of the fluid during temperature changes. Here is a drawing of a simple closed loop that will do what you want. The header pipe will leave a vapor area that will allow for expansion. Locate the top of the header above the highest point in the loop. Of course the pump and header pipe could be located in the reservoir itself, and piped to the external chiller. The roll of tubing and connecting tube should be 1/2 inch.
Tag me if you have any questions.
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Got it. That’s certainly more elegant than a bucket, but at least it looks like I was thinking in the right direction. Thanks!
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