Sieve,
Click to make pic bigger...
Looking at the pic above, here is a quick rundown on what I believe your valves are doing. Please confirm that I have the labels you gave me, associated with the correct valves...
The pipe labeled H sucks water from your pool skimmer and allows you to remove the debris that float on the surface of the water.
The pipe labeled G sucks water from your Main Drain... This takes water from the bottom of your pool and helps circulation.
The pipe labeled E sucks water from your Spa's Drain. This would allow you to remove the water in the Spa...
The pipe labeled F sucks water from your Spa's skimmer... (Not sure that is what it is called???)
The pipe labeled D goes to (Not sure at this time...) I assume this pump is for a water fall or some other water feature, but you did not say...
The pipe labeled B sends chlorinated water to some water feature.. Maybe the spillover from your spa into the pool, or bubbler, or???
The pipe labeled C sends chlorinated water back to the returns in the pool wall (the eyeballs).
The pipe labeled A sends chlorinated water back to the Spa jets (Therapy jets) ...
The valve labeled I is called the "Intake or Suction" valve and it allows you to select between the Pool mode (pipes G and H) or the Spa mode (pipes F and E)
The valve just right of the letter A is called the "Return" valve and it allows you to return water to the Spa (pipe A) or the Pool (pipes B and C)
You will need to experiment to see if this is correct.. Try this..
1. Turn the valve by A so that the handle points away from pipe A. This should turn off the Spa jets
2. Turn valve I so that the handle points away from pipes F and E... This should stop water from leaving the Spa.
3. If this results in the Spa filling up and overflowing into the pool, then turn the valve between B and C so that the handle points to C. This will turn off pipe B and I assume stop the spillover or turn off some other water feature.
If you can try the above and let me know what happens, we can move on from there...
Assuming you have not fallen asleep yet..
Thanks,
Jim R.