I just had a new Jacuzzi installed as part of a bathroom remodel and
find that my 50 gallon hot water heater does not have sufficient
capacity to fill it with hot water so I am looking for possible
solutions. The current gas hot water heater is only two-years old and,
except for the jacuzzi, provides plenty of hot water for my wife and
me so I am reluctant to just replace it. The other thing to factor in
is that we had a recirculating pump in the line to the bathroom
because it is a long run from the hot water heater and took a very
long time to get hot water up there. Now it is instant. The reason I
mention this is that I understand that supplemental units usually turn
on when there is water flow in the line and I would not like to have a
supplemental unit running all the time.

Are there supplemental heating units that would work in this
situation? Perhaps ones that turn on only when the temperature in the
line drops below a set limit?

Any help or suggestions for making this work would be greatly
appreciated. I know that I could just replace the current unit with an
80 gallon tank but that seems a waste of money and energy since the
Jacuzzi will not be used a lot.

Thanks in advance - Joel