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Old 06-07-12, 07:46 PM   #38
GaryGary
Apprentice EcoRenovator
 
Join Date: Nov 2008
Location: SW Montana
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Quote:
Originally Posted by Daox View Post
The return pipe will not be full of water on the way down (it'll drain faster than the pump can pump). Therefore it can't create any suction to assist in pulling the water up. Even if the pump could keep up, it would then also not create suction because the pump would still be pushing everything along.
Hi Tim,
On a drain back, my understanding is that the return line should run full, and if it does not something like a partially closed valve should be put in the return line near the tank to offer enough flow resistance to keep the return line full.
I have to do this on my Solar Shed system because the return line is short and direct -- without the valve it won't run full. In addition to increasing the pumping head requirement when its not running full, it also makes quite a bit of of noise.

Gary
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