I pretty much do the same except my number is about 5 psi rise on the gauge. I assume the left pipe is the return to the pool, the right one is the feed to the panels, and the bottom is the feed from the pump. It looks like the valve is set slightly restricting the left pipe which should increase your gauge psi a little and force some water through your panels. If it's warm and you don't require any heat just move the valve so the "off" is in the 12 o'clock position which will open up the pipe to the pool and none will flow to your panels, assuming they are high like on a roof. You could also move "off" over to the solar feed side. When you want to heat the pool put the valve in about the position it's in. This will slightly restrict some of the flow back to the pool and force some water through the panels. To see if it's enough, first feel your panels with you hand before turning on the pump. Use a little common sense here as they can get hot. Then turn on the pump and feel the panels again. They should feel cool to the touch. If not turn the valve counter-clockwise until they do. The objective is to get as much as possible out of the panels without putting too much pressure on them. I've done a lot of tuning with a temp gun on mine but this simple procedure will get you pretty close to where you want to be.