Plumbing quesetion for separate pool and spa without spillway.

[okayfine]

We are in the Northeast. We just poured concrete slab for Endless Pool. We made the slab a bit bigger to accomodate a separate hottub. I have "free electricity" from my solar panels (I generate more than I use), so I've been looking at Arctic Heatpumps - they are a bit pricy, so I'm trying to see if it is possible to design the plumbing so it can service both bodies. This would simplify managing the water chemistry which is another big motivation.

The pool and hottub are separate (no spillway). Most dual zone setups I've seen are designed with spillways in mind. So is there any reason I can just directly connect the 2 bodies with an appropriately sized pipe with a valve? See diagram 1.

When normally, the system would filter and heat both bodies at 80 degrees, and the water would flow as noted in green lines in diagram 2. When we want to use the hot-tub, water would flow as shown in brown lines in diagram 3.

First time owner, so any critique / suggestions welcome! Thank you so much.

 

[HermanTX]

The placement of the connecting plumbing between the 2 bodies of water is critical. If it is low (as shown in the drawing) the bodies will seek an equilibrium level. This why a spa overflows to a pool. But also why an elevated spa has a check valve to prevent this equilibrium when the pump is off.
You also need to think about the opening and closing sequence of the 3 way valves to switch between the different modes.
Others may have ideas.

 

[ajw22]

You are effectively creating a spillway with your pipe connecting the pool and the spa.

So, you have created a single body of water with shared equipment.

Your issue will be getting sufficient flow through the pipe to meet the pump suction demand. As you have it drawn, the pump will probably drain the spa with insufficient water flow through the pipe to keep up with the pump demand.

A spillway uses gravity and can provide an unrestricted flow between the spa and the pool.

And single body setups flow water the other way. Suction comes from the pool and returns it to the spa.

You need to reverse the flow and create a connection between the pool and spa that can meet the maximum pump flow.

 

[ajw22]

Are you going to use automation or manually turn valves to switch between pool and spa?

 

[okayfine]

Are you going to use automation or manually turn valves to switch between pool and spa?

I was going to turn the valve manually. I can ask the heatpump maker to do a simulation to see how quickly it can turn 500 gallons of 80 degree water to 104 degrees, and assuming that that's reasonable, I don't think I need automation to get the heat the hottub.

How much does a motor valve and an automation controller cost, btw?

Your issue will be getting sufficient flow through the pipe to meet the pump suction demand. As you have it drawn, the pump will probably drain the spa with insufficient water flow through the pipe to keep up with the pump demand.

The connecting pipe would be about 2-3 feet in length. 2.5" pipe should be sufficient? Pool pump would be sucking about 12-15 GPM, I think (heater wants 11.3).

The pool and the hottub will be at the same height, so water finding an equilibrium level wouldn't cause any issues I think.

 

[ajw22]

What heater are we discussing?

I think you need much more than 12GPM.

Nothing will be sucking through that connecting pipe to encourage a flow through it.

I wish you luck with your project. You will get an education about hydraulics.