Top hose SHOULD be for hot out, not cold in. Cold water goes in the bottom and hot water comes out the top. See attached pic. Sounds like you have Option #2 at the upper right.
I'd guess one of the two valves isn't completely closing off to the HWH. Could be some debris in one of them. You could try refilling the system and running water through them. Or remove the valves and check them.
Or just live with it, if it's not a lot of AF.
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1988 Coleman Sequoia - popup (1987-2009) - outlasted 3 Dodge Grand Caravans!
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