Explain my pool / spa plumbing system?

[mikelehen]

I recently became the owner of a pool and "spa," but the spa is a bit strange (it's just a tiny ~300 gallon fiberglass tub alongside the pool), and I haven't figured out how to actually get it to filter along with the pool water.

The pool and spa are on the same plumbing system (one pump, one filter), but currently the suction and return valves for the spa are shut off, so only the pool is being filtered. This works great for the pool, but I'm trying to figure out how to incorporate the spa into the plumbing system.

The problem is that when I open the suction and return valves for the spa, water circulates but the water level of the spa starts dropping (i.e. I must be sucking more than is being returned). It seems to drop indefinitely (it'll continue dropping well below the pool's level). If I turn the suction valve so it's only partially open, I can get the spa to almost maintain its level, but over the course of an hour, it'll either raise or drop by an inch or so depending on where exactly I have the valve.

So my question is basically: how is this supposed to work? In particular:
1. Can I somehow get the spa to maintain its water level while both the pool and spa are being filtered?
2. If not, am I supposed to just filter one at a time and not both? That would make some sense, since you'd probably have them at different temperatures normally (though I have no heater in the system for either the pool or spa)?
3. If I'm supposed to only filter one at a time, how would I do that automatically without having to turn valves constantly to change which one is being filtered?

One other potentially relevant piece of info: The system initially included a solar heating array on the roof, but it's been defunct for a long time.

I'd also be curious if anybody has any other insight into my system. Have you seen a tiny "spa" like this before? Is there a name for it?

Thanks!
-Michael

My Pool and Spa:


Plumbing:

 

[jblizzle]

Welcome to TFP!!!

Is there a connection between the spa and pool directly? Obviously no spill over, but is there a pipe that connects them that would allow the water to mix? If not, then I am not sure there is an easy way to keep them chemically balanced together and your may have to treat them separately ... pour design.

You could automate this some, but you would have to change the plumbing to use true pool 3-way valves that you could put an actuator on and get an automation system to change from pool to spa mode daily. You would also likely want a way to automate the chlorine addition to the 2 bodies of water as well.

 

[mikelehen]

Thanks! There is no direct connection between them. There are just the suction and return pipes that meet each other in the equipment room. Perhaps the intention was to just run the pool during the summer and spa during the other months. The actuator / automation system sounds interesting, but a non-trivial project so I'll probably just drain the spa for now. Since it's not heated, it's not that useful anyway.

Thanks for confirming it's likely just a poor design and I'm not missing something obvious.

 

[mikelehen]

Next question (related to my silly "spa")... It has two return jets, and both have these air tubes sticking straight up on the outside that I guess pull air and turn the returns into aerated jets (if I cover the hole with my finger, I stop getting bubbles out of the return jet). Anybody know anything about these? Is this a standard design? I couldn't find anything about them on the internet.

Would there be any harm in leaving them "aerating" all the time, or should I plug them when not in use or something?

 

[jblizzle]

I have a similar design.You can leave them open, although the extra aeration will raise the pH.