Swimming pool fluid water dynamics

Hi All,

I live in Florida and have a typical mar cite in ground 15’ x 30’ pool with a spa. I have 2 water pumps: one 50lb pressure spa pump that just has a circuit from pump to spa and returning water back to spa pump for 6 jets and to heat spa. The other pump is a typical 1hp 5lb pressure pool pump that has a separate closed circuit to 3 pool outlets for circulation and back to pool pump using an in line salt water system. This closed circuit does NOT utilize the Electric Pool Heater that the SPA circuit does.

So we have 2 separate water flow circuits: one for heating the Spa and one for circulating the pool and Spa with NO heater connected with pvc pipe.

I had asked the pool builder to use the electric heat pump to heat Both pool and Spa but he said most people just want the SPA heated only in Florida. Needles to say I was pissed.

Now here is the technical question I have. Would it be possible to utilize a 2way plastic connecter from the Heater outlet to SPA connected to the Heat pump and plumb in a 1.5 " pvc pipe straight to the Pool Return to Spa pvc pipe? I could have the heater side outlet open to Both SPA and Pool or just to Pool or neither and just have original Pool pump circuit used leaving Spa to Spa heated circuit closed altogether?

The reason I hesitate to make this connection is that if I connect the Spa only circuit to the Pool to Pool and Spa circuit, the water pressure may be compromised and there wont be enough circulation.

I know you will be asking about all these variables but I must know if making a simple bypass connection between Spa circuit to Pool circuit to utilize the heat pump to heat either or both circuits will work because all the pipe are under pressure and using one or the other or both will compromise the flow to either circuits.

Get to know the folks over at http://www.troublefreepool.com - some great folks who know pools and are willing to share. They sell water testing kits, so expect a bit about knowing every variable that can be tested.

I have never heard of a 50 psi system, so I’m not going to guess.

To be absolutely safe, set up valves on both the input and outlet ports of the heater - and use one-way valves to prevent cross-feed.
As long as you remember to switch both valves - keep the input from the pool connected to the outlet for the pool, and spa in is always spa out, you won’t be mixing the systems.

Of course, if the builder sized the heater for just the spa, it probably will not be adequate to heat the pool. Look around Trouble Free and ask (Pumping Station forum) for a formula for BTU-to-Gallons-to-temp rise.
If the heater can’t raise the pool enough to bother with, calculate the required BTU and install a new, larger heater (between filter and return line).

And run this by Trouble Free for expert opinons.