One skimmer only. Unless buried in the yard somewhere there are no mysterious valves. There are only two three-ways at the pad - one for spa/pool suction and the other for spa/pool return.
I know all the flow is currently from the skimmer because it accidentally sucked up a floating rubber toy once while the basket was out and when that stuck to the pipe the pressure dropped to zero at the filter. I thought maybe the main drain might be tied to the spa drain, but when I set to spa suction and spa return there is zero overflow from the spa. That lever that used to be at the bottom of the skimmer, and what appears to be some sort of scale on the right, have to have been for something.
