I must admit I'm having a hard time picturing it. Any head should sink and air must be captured somewhere that you're not purging. You are not by some chance using a "floating hose"--my Polaris 165 has one (haven't used the Polaris in years). Do NOT add lead weights to the head, though a small plastic-covered free weight or dumbbell could be zip-tied to it...just a thought. I wouldn't use an uncovered metal free weight though.