In the home I'm presently living there's 2- 50 gallon electric water heaters opposite ends of house; (aprox. 50ft apart). One takes care of kitchen sink and 2 full baths with a long pipe run to termination. The 2nd heater has a slightly less distant pipe run which takes care of a laundry (tub and washer) and Master bath which contain a Shower, double sink, and 84 gallon whirlpool tub. I was hoping the 50 gallon water heater taking care of the Master bath would allow the tub to fill @ aprox 120 deg. it will 2/3 fill w/ hot water. The rest needed we fill it with hot water from stove! Not convenient. Also; the other end w/kitchen and 2 baths, achieving hot water is slow and a 60 ft pipe run to termination. I considered to replace the WH for the master bath w/ the whirlpool tub w/a tankless unit for the master bath. Then I considered to just use a higher gpm Navien tankless w/ built-in circulator and just replace both water heaters. But then I thought, why not just use both existing water heaters there with a circulator; allow the 1st HTR to fill w/ cold , take hot to 2nd WH cold side, then 2nd WH hot side back too 1st WH drain valve to keep circulation using 3/4 for circuit main ? I figured I could get a 100 gallons at hand which is circulating thru both units, and use for whirlpool tub when needed. I figure the 2nd WH would be only maintaining temps as a holding tank, and both would be still be cost effective when not in unusual use. Please tell me the drawbacks of this system, or how to be connected in different way to work efficiently, tankless or other way. There's only 2 of us , so not big daily hot water demand. A diagram would be helpful. Thank you; and please reply. Howard.