New house: Question about long lag until hot water and use of circulator

leejosepho said:

Natural convection or "gravity flow", at least as I know it, for anything related to heating is far from efficient. So yes, your line might stay warm that way, but you will likely need a circulation pump if you want truly-hot water quickly available at the tap.

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It makes sense, all my mental excercise is just a technical discussion. I cannot act on speculation. The water tends to move slow. Routed through an unheated space, even with pipe insulatioin, will probably have so much heat loss that it won't do any good. It will change the situation to really-really cold water for a few minutes to very cold water for a few minutes.

hj said:

Gravity circulation will work great, UNTIL the first place the pipes turn downward, such as a jog under a beam in a basement, or going into the concrete floor.

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What do you mean with that statement? Please clarify/educate.