Follow up: Client called me on Nov 02 stating that water had been running off the roof. The client isolated the system. Having taken pictures of the collector and associated plumbing I could visualize and ask the client specific questions about where the system was leaking. I had the client open the valves sending water back to the collector. I then instructed the client to go look at the collector from ground level. I then asked the client to tell me exactly where the water was coming from. (Note that I was able to instruct the client what to look for since I had the photograph.) The water was coming from the freeze valve. Told the client to isolate the system and that I would come by in a few weeks and determine the exact problem. Pretty certain it is the freeze valve.
Dec 02 Visit to site. Ambient temperature was in the 70s. Owner had isolated solar loop. Opened solar loop and discovered that freeze valve was dribbling water. Provided client with a new freeze valve. Added Teflon tape and instructed client on how to replace valve. No ladder to get on roof at the time. Client did not want me on his roof. Insurance concerns. Client is mechanically inclined and will replace the valve.