Lately I've been getting a lot of air bubbles coming out of one the returns. This only happens when the valve is switch to the solar panels. When not on solar, no bubbles. Now I've always had some air bubbles when the solar is first switched on as all the air in the solar panels is flushed, but that only takes a minute or two. Now the bubbles are non-stop. I suspected I might have a leak, but after climbing up the roof, I saw no evidence of any leak, so I'm stumped as to where the air is coming from.
Alex
Alex
