Well, I'm still learning things, even after a long time diving and servicing equipment!!
I have long espoused the belief that adjustment knobs were a "nice to have" but actually totally unnecessary. As long as you have a valve that doesn't crack when the diaphragm is lowest in the water, you're good to go. Except maybe with a giant stride off the boat. Right?
Wrong. I don't yet know why, but I'm wrong. At least for those of us that tinker and tune their regs "hot".
So I'm on my bucket list dive trip stuck on a liveaboard for 12 days. Having brought along tools (of course!), I end up running point for minor repairs like a spool or hose leak from a broken o-ring.
A guy comes up and says, "My reg is freeflowing just a little, when I turn my head to the side." He denies that it freeflows when he looks straight down. I think, "Huh?" So we put an IP gauge on and his first stage is giving 145 psi. A little higher than I'd like, but within spec. So we gently submerge his second in a cookpot of water, and the valve begins to hiss at about 1" below the surface. Bingo!
One twelfth of a turn on the orifice, no lever rattle, 1.2" on the dunk test and we're good to go! Ain't I smart? He buys me a beer.
Next day, he comes back and says, "It's happening again". So we dunk the reg and it's still 1.2" and I suggest maybe he's not quite closing his glottis when he looks to one side, and it's just freeflow from his lungs. He says not, so we up things to 1.4" with the microadjust in the knob and he goes away happy. Indeed, he confirms that it worked fine for the rest of the trip. I remained skeptical but chalked it up to personal preferences.
So two days later, I'm diving with my hot-tuned Atomic second (1.0"), and when looking face down, there's no valve leak. But I turned my head to one side, and sure enough, there were a few bubbles going out the exhaust tee! I made sure to close my glottis and it seemed to disappear, so I figured I was getting a little sloppy with my technique. But it occasionally recurred, and I noticed that on some occasions, when I was sure my glottis was closed, or more pointedly, when I stuck my tongue in the mouthtube, the reg would still gently bubble, and in a position that wasn't the worst for case geometry fault!
Turning the adjustment knob a half turn made it go away.
I don't know why, yet. My initial conjecture is that (apart from failure to maintain a closed glottis between breaths - and who does that all the time?) the leak might be due to an open valve from inhalation, that then continues to freeflow gently when the top of the exhaust valve is close to the diaphragm center, allowing continued egress of gas because the internal case pressure can't rise enough to overcome cracking effort. In retrospect, I should have tried a forceful exhale, to see if that stopped it, but I didn't think of it. I dunno, really. But the phenom was reproducible, and I've been pondering it for the past week until I could get back on Scubaboard.
So, it's real if you hot-tune your regs. For me, the lesson wasn't to stop hot tuning, because I love an easy sip of air. Instead, I now pay a little more attention than I have for the past 30 years when I'm looking sideways under a ledge at a shrimp. I think over the next week of diving I ended up temporarily adding a half turn three or four times, though I always returned it to its easiest setting for the rest of the dive. And I even ate crow and told my "customer" that he'd taught me something. But I didn't buy him a beer.
I'm still learning.
Anyway, I'll stop dissing adjustment knobs from now on. They actually have a purpose.
I have long espoused the belief that adjustment knobs were a "nice to have" but actually totally unnecessary. As long as you have a valve that doesn't crack when the diaphragm is lowest in the water, you're good to go. Except maybe with a giant stride off the boat. Right?
Wrong. I don't yet know why, but I'm wrong. At least for those of us that tinker and tune their regs "hot".
So I'm on my bucket list dive trip stuck on a liveaboard for 12 days. Having brought along tools (of course!), I end up running point for minor repairs like a spool or hose leak from a broken o-ring.
A guy comes up and says, "My reg is freeflowing just a little, when I turn my head to the side." He denies that it freeflows when he looks straight down. I think, "Huh?" So we put an IP gauge on and his first stage is giving 145 psi. A little higher than I'd like, but within spec. So we gently submerge his second in a cookpot of water, and the valve begins to hiss at about 1" below the surface. Bingo!
One twelfth of a turn on the orifice, no lever rattle, 1.2" on the dunk test and we're good to go! Ain't I smart? He buys me a beer.
Next day, he comes back and says, "It's happening again". So we dunk the reg and it's still 1.2" and I suggest maybe he's not quite closing his glottis when he looks to one side, and it's just freeflow from his lungs. He says not, so we up things to 1.4" with the microadjust in the knob and he goes away happy. Indeed, he confirms that it worked fine for the rest of the trip. I remained skeptical but chalked it up to personal preferences.
So two days later, I'm diving with my hot-tuned Atomic second (1.0"), and when looking face down, there's no valve leak. But I turned my head to one side, and sure enough, there were a few bubbles going out the exhaust tee! I made sure to close my glottis and it seemed to disappear, so I figured I was getting a little sloppy with my technique. But it occasionally recurred, and I noticed that on some occasions, when I was sure my glottis was closed, or more pointedly, when I stuck my tongue in the mouthtube, the reg would still gently bubble, and in a position that wasn't the worst for case geometry fault!
Turning the adjustment knob a half turn made it go away.
I don't know why, yet. My initial conjecture is that (apart from failure to maintain a closed glottis between breaths - and who does that all the time?) the leak might be due to an open valve from inhalation, that then continues to freeflow gently when the top of the exhaust valve is close to the diaphragm center, allowing continued egress of gas because the internal case pressure can't rise enough to overcome cracking effort. In retrospect, I should have tried a forceful exhale, to see if that stopped it, but I didn't think of it. I dunno, really. But the phenom was reproducible, and I've been pondering it for the past week until I could get back on Scubaboard.
So, it's real if you hot-tune your regs. For me, the lesson wasn't to stop hot tuning, because I love an easy sip of air. Instead, I now pay a little more attention than I have for the past 30 years when I'm looking sideways under a ledge at a shrimp. I think over the next week of diving I ended up temporarily adding a half turn three or four times, though I always returned it to its easiest setting for the rest of the dive. And I even ate crow and told my "customer" that he'd taught me something. But I didn't buy him a beer.
I'm still learning.Anyway, I'll stop dissing adjustment knobs from now on. They actually have a purpose.
