Pex sizing for hot water recirculation loop

[MartyW]

I need some advice on sizing pex pipe on a dedicated hot water loop I am installing in my home. It is a 2,400 SF single story ranch home. The basement is unfinished and I am running the lines in the basement ceiling before I finish the area. A sketch of my initial plan is included.

• Distance from water heater to farthest fixture is approximately 65’
• Piping will be pex A with cinch fittings
• I have initially planned to run 1”pex pipe until I reach the last fixture, then ¾” pex pipe back to the water heater
• Pump is Grundfos UP15-10
• Water will reenter the heater through a T in the cold water inlet pipe

I was thinking 1” instead of 3/4” for most of the loop because I know the fittings reduce the flow and I wanted to minimize this. However, I am concerned that the volume of water in the 1” pipe that I am circulating might be excessive and cause higher reheating costs. There might be other considerations I am not aware of. Any recommendations on pipe size? Any other feedback on this plan?

Also, I am buying a new water heater for this system since my current model is over 15 years old. I plan to install a 40 gallon natural gas tank heater with atmospheric venting. I am also open to feedback and suggestions on the water heater. I am wondering about a larger tank size and maybe power vented. There are only two adults living in the house for the foreseeable future. The purpose of power venting would be for gas efficiency and to eliminate the last atmospheric vent in the house.

Thanks!

 

[Breplum]

You should be fine with 3/4" PEX.
Over 20 year timespan, it could be argued to have a nice Navien NPE A2 with 96% AFUE and built in pump for a better system. Or upsize WH and go with heat-pump to eliminate greenhouse gas pollution.

 

[Sponsor]

 

[MartyW]

You should be fine with 3/4" PEX.
Over 20 year timespan, it could be argued to have a nice Navien NPE A2 with 96% AFUE and built in pump for a better system. Or upsize WH and go with heat-pump to eliminate greenhouse gas pollution.

Thank you for the response and information. I looked at some heat pump water heaters. They seem super efficient. However, as I understand it they don't work with a recirculation system. Is that correct?