I used a configuration almost identical to one I found here on this site to set up my 8 2x20' solar water heater system. Since setting it up correctly, it's been awesome, and the water temperature is now actually higher than the average ambient air temp, right around 90 degrees, which is great for our cool evenings.
I have 2 sets of 4 panels together, as shown in the image attached, everything connected together.
I put a release ball valve at the end of each set so I can release the air. It works quite effectively, but it's a manual process and sort of a pain. I tried a 75psi relief valve I found at Lowes, but that's just too much pressure required to do anything.
I ran all 1 1/2" pipe for the system, and the valves are the same. I can easily reduce to whatever I need to, but I'm looking for advice on what I can add so that when the system comes on, it will bleed the air out automatically without dumping too much water. Should I add a pressure relief valve after each ball valve, and if so, what size/psi?
BTW, the current ball valves are in a T configuration, so there is a T, which the water flows through, and UP to get to the exit for the valve. Like ____||____ (the valve is on the Up part.)