Our single-story home (on slab) is 2500 sf and the master bath is on the farthest end of the house from the water heater. I recently replaced the old 50 gal tank heater with a Rheem 200gph outdoor natural gas tankless unit. Our master bath has always had poor (hot) water pressure - I am currently gutting it and adding a larger shower. The new Rheem unit is great for the rest of the house, pressure to the master bath is still an issue as well as the long wait for the hot water to reach it. I want good pressure and quick heat in the new shower.
The main water line splits right outside the master bath. The cold 3/4" line comes in under the slab there so cold pressure is great. When I installed the new tankless unit, I ran the 3/4" hot return up in the attic where it goes down to the laundry, then guest bath (under slab), then kitchen (under slab), then finally back to the master (under slab - of course all after being reduced to 1/2")
Should I take advantage of the 3/4" cold inlet in the master with plenty of pressure from the street and add a small tankless in a closet? This would most likely need to be electric as I don't plan to have the nat. gas line run all the way around the house from the valve by the new tankless unit. I probably have room in the breaker panel to do this but it's just as long a run for power as it is for the hot water.
Do I tee into the new 3/4" hot water return in the attic from the existing tankless and shoot straight over to the new master bath (insulating all the way), thus bypassing the 1/2" hot water returns under the slab.
I would guess the run would be about 40-50 feet or so.