We had a re-circulation pump installed in our 'stick' house after an in-slab hot water line running to the master bathroom began leaking down through the slab. The old lines in the slab were disconnected and new hot and cold lines were run through the attic (the only economically feasible alternative).
A third line was installed in the attic running from near the end of hot water line back to the cold water inlet of the water heater. This third line has a small re-circulation pump at the water heater, taking water from the third line and pumping back into the water heater.
Our home water heater is near the kitchen (and the coffee maker!) so in the morning we turn on a timer connected to the re-circulation pump, get a cup of coffee, and head back to the bedroom for a shower. Less than 5 min the water at the bathroom is hot. After 10 min the pump shuts off.
With the third line, we only needed the additional line, pump, and timer. No other valves etc. were necessary. I don't have my trailer yet, but adding a line back to the fresh water tank and a manual valve (probably under the bathroom sink) seems like a reasonably easy mod to save water.
Sherm & Terry w/rescues Steve (std Poodle) & Eydie (min Schnauzer)
2015 Jay Flight 27RLS (Camped: 102 nights 2015, 90 nights 2016)
2006 Ford F350 6.0 PSD, Lariat, 4WD, CC, LB, SRW, auto., Camper pkg.