Recirculation Loop Design Question

[Aberrant]

Trying to determine the best design for my 2 story re-pipe. I'd like to design with a recirculation loop in mind. I'm using a trunk/branch system using 1" pex for the trunk lines and branching off 1/2" pex to fixtures. I have a 1" trunk off the main trunk that runs to the second floor to serve 2 bathrooms and a washing machine. Does that line need to be a continuous loop that runs up and loops back down to the main trunk in order for a recirculation pump to work best/most efficiently? Would it be fine to leave it as a dead end branch and just loop back to the water heater at the end of the main trunk line? Attaching two rough sketches showing my thinking.

Design A:

Design B:

 

[JoeJee]

I’m not a plumber but I would lean towards A. You are likely to have a lot of water in that 1” pipe up to the second floor. It would take some time to get hot water if only using a single lav. B would be better than nothing though.

 

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[John Gayewski]

Yes A is better, but at some point it can slim down. It doesn't need to be 1"the whole way. The other option is to run a recirc back down to the water heater from the second floor and one from the end. You balance the flow with a balancing valve where the two lines meet back up at the water heater.

Insulate, insulate, insulate. You lose a lot of heat through these lines if there's no insulation it's many times worse.