I think I've been keeping my 3 way Jandy valve in the wrong position when I wanted the solar off and now want to check my logic here.
The 3 way valve can be rotated 360. When I wanted solar off, I would position the valve such that the gate was North and blocked flow to the vertical pipe. However, if I did this while the pump was running, I trapped water in the feed pipe.
Is it OK instead to turn the valve so that the gate is South (toward the X) and not blocking any flow to any pipe. Then the water takes least resistive path and avoids the solar even though the path is open. This would allow the solar to drain completely.
Either way, when I want the solar On, I just turn the valve so that the gate is North East allowing some flow both ways.[attachment=0:3mvram2v]solar.gif[/attachment:3mvram2v]