purge valve flaw

I bought this to use swimming laps. It doesn't work for that at all. If I just sort of drift around slowly, like I am trying to watch a reef, or fish, or something, it seems to be fine. But whenever I try to actually swim and start moving at any speed, it's like the turbulence causes the purge valve to open and I'm sputtering to get breath through the water filling the tube and it's not that I'm ultra speedy swimmer. I'm not. I can't even just go on a kickboard or it's too much speed for this purge valve to seal. (and I've cleaned it several times, so that's not the problem.) So, unless someone has a fix for this, (which I would greatly welcome) this snorkel is fine for floating but not acceptable for swimming laps.

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