Pool heater question

Central Fla.
I want to build a spa next to my small 16,000 Gal in-ground screened in pool.
The bottom of the Spa will be above the pool deck.
Is there a heater that will do both my pool and Spa?
Would I need to get 2 heaters?
Could I set up the heater plumbing so it heats the spa and the water over flows into the pool thus heating the pool too slowly, and the fresh water is drawn from the pool?
Either way i do want my spa to draw water from the pool using 1 Pump for both the pool and spa.

What I want to be able to do.
1) heat just the spa.
2) heat the spa and pool
3) heat just the pool

What would I need to make this work and what are some different ways that I could approach this?
This should also make it easier to keep the spa water balenced?

Quite simple to do really. Its a matter of a couple 3 way valves for pool / spa returns and plumbing in the heater. You can go all out with some automation equipment such that at the touch of a button on a remote control you hit SPA and the valves and heater all come on at the same time. You can then hit POOL and the valves rotate back so that the heater goes off and the pool returns are flowing.

I do quite a bit of equipment upgrades to the automation equipment, its a lot of fun as well as convenient for poolowners.

Feel free to contact me for more info if you'd like to discuss.

-Jeremy
Florida Leisure Pool & Spa

Hi Jeff
consider going with a heat pump
it's more efficient than most other types of heaters & yes you can do exactly what you wanted to do

"What I want to be able to do."
1) heat just the spa.
2) heat the spa and pool
3) heat just the pool

I have a Summit brand heat pump.
it does all three options
( pool & spa can have different temperature settings)

The problem with using a heat pump to heat the spa is that it takes too long. Heatpumps are efficient at maintaining pool temperature but lousy at quickly raising temperature.

I use a heatpump to keep the pool water at 85 and a gas heater for when I want to use the spa. I have a 400K BTU propane heater that takes about fifteen minutes to raise the spa temp temp to 100 degrees. A heat pump would take several hours - if not more.

Good Luck