PEX repipe - home run or hybrid and recirc

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Seattle, WA

I'm currently planning a repipe of our home from a very shoddy T&B setup to a newer pex setup (poor piping and poor design. If I turn on a cold tap ANYWHERE in the home, someone showering in the master bath at the end of the trunk loses ALL hot water.) We live in a tri-level where I can access the laundry room, HWH and everything kitchen from a crawl space. There are 3 bathrooms which I will get to by going from the crawl space, through the garage (when all drywall is removed) and to the bathrooms. The three bathrooms are all clustered together (two full, one half.)

For designing the system, I have two main questions:

1.Remote manifolds: part of my goal here is to make it so that someone can shower without worrying about a toilet being flushed. Do remote manifolds pressure balance everything just as well as a central manifold? That is to say, if I run a 3/4" line with remote manifolds coming off it, would someone flushing a toilet at remote manifold #2 deprive remote manifold #3 of pressure? Main advantage I see here is how simple the recirc loop would be.

2. If I go home run, could I still pull off recirclation? We have a RUR98in with a built in recirc pump; the pump will run until the return water temp is within 12F of the target temp. My idea here is to hook up recirculation for the three bathrooms that are clustered together (two full baths directly above a half bath). I would T off a return line from each fixture to a manifold located between the 3 bathrooms, and then run a 3/4" return line from the manifold back to the HWH. If I understand this right, I'll need a check valve on each fixture's return line...but everything should be OK since all of the home runs would be roughly the same length, within a few feet of each other. Is this a sound plan? (I'd be plumbing return lines for three faucets and two bathtubs)

Some extra info:
I'll be going F1960 - I got my hands on a used Milwaukee expansion tool.

Our water supply line from the street is 1" type L copper. Pressure is roughly 63PSI. The 1" line is narrowed down to 3/4" close to the water heater. The lines then split directions; a T&B 3/4" line goes to feed the three bathrooms. (maybe 35' of 3/4" line?) 1/2" trunk lines go off to feed the kitchen (faucet, dishwasher, fridge, pot filler) and backyard spigot (which is 3/4", so they just expanded 1/2" to 3/4" by using marine epoxy to join two brass MNPT fittings together. They win a prize!)

Michael Young

In the Trades
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North Carolina
"marine epoxy to join two brass MNPT fittings together."
are they freakin’ nuts!!

My house had the same problem. When I repiped it I made one giant loop with the hot. I was going to install a circ., but by making a loop, that automatically increased the available hot water to the bathroom because I was getting a double-feed through the loop. It worked great, so i never went back to install a circ.

RUR98in. sweet little system! Yeah. use the circ logic controller and you'll be fine
Hey, wait a minute.

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