How to air lock main drain in IG spa with no diverter valve?

[bov188]

I recently inherited an in ground pool/spa and I'm a bit confused about the plumbing setup/main drain and how I would air lock it.

Some info on my pool setup (Also see attachment for pics of setup):

• Inground vinyl pool/spa
• 1 pump, can only pull from pool OR spa, not both (has to be controlled with valves on suction side)
• Pool
  • 2 skimmers
  • 2 returns
  • NO main drain
• Spa
  • 1 skimmer
  • 6 returns
  • 1 drain on floor
• No spill over, or extra features
• No dedicated vacuum line

On the suction side, there is a valve/actuator to change the suction from pool to spa and vise versa.
On the pool suction side, there is another 3 way diverter valve to isolate 1 of the 2 skimmers, or have both open.
On the spa suction side there are 2 pipes coming up from the ground and they join into 1 PVC tee but there is no diverter to isolate the skimmer or main drain.

So my question is, how would I air lock the main drain in my spa if I cannot isolate the main drain? When I blow out the lines I can see bubbles coming from the main drain, but there is also air coming out of the skimmer.

Don't I have to isolate the main drain to create an air lock? Or am I wrong on this?

 

[kimkats]

I am not sure so here is a bump.

 

[Catanzaro]

Do the covers in the SPA come off, which will allow you to work backwards? You could always use the blow-thru plugs. A lot depends on the air volume. The cyclone would be able to push enough air through the system to have both areas bubble long enough where you can create the "air lock". Then you can try to add an extra plug in the pump basket.

Considering you have Pentair 3 Way Valves, take the skimmer valves and loosen the wing nut. Lift up and turn towards the drain/spa. This way, the air will only travel towards the drain/spa and away from the skimmers.

A lot of times, one must think outside the norm. Thanks!