It's a 3.5, I think I will run another DW flush. I see in the book that if you have 3rd zoneheat, that adds another 2qt. I don't have that, but made me think the regular dual zone may be holding most of what I am missing. I ran the heat during flush so its cycling. Just might not be draining. If there is another plug, I doubt I could even get to it doing this on the garage floor. I will look online later today,since its down till I get another clamp.