My husband and I recenty replaced our 65 gal hot water heater with a 50 gal model thinking this would provide sufficient hot water since there are only 2 of us in the house. However, when I use my jacuzzi tub (a heart shapped model) I find that the water is running warm not hot at the end of the filling process. Is it possible to add a second (15 gal) tank to the existing system?