Upside down regulator - how wet?

[Texasguy]

Say you put your regulator facing up surface (like if you would be on your back towards the bottom), how wet does it breath? What brand do you have?

 

[tbone1004]

no different than it does in any other orientation, but I have a Poseidon.... If it is diaphragm down it will freeflow into my mouth similar to any other regulator with its diaphragm straight down, cracking pressure is essentially negative at that point due to venturi.

Most of the other ones will breathe very very wet if the diaphragm is straight up. why?

 

[Akimbo]

Small amounts of water often leaks into the regulator around the lips on inhalation. We don’t notice it because it goes out the exhaust valve most of the time. You really notice it when you position the exhaust mushroom valve higher than your mouth. That is true with a conventional regulator or a side exhaust… water flows downhill.

You can usually solve the problem by exhausting the water after changing position and then tighten the lips around the mouthpiece before returning to the exhaust-high position.

 

[stuartv]

I have experimented with swimming around facing directly up. I have not noticed my reg breathing wet at all. But, it did became noticeably harder to breathe. Not that it was HARD to breathe. Just hardER to breathe than when facing down. My understanding is that that is normal due to the pressure differential between the 1st and 2nd stages. Normally, the 1st stage is basically as high or higher in the water, so the pressure is the same or less on the 1st, as compared to the 2nd. But, when you float on your back, facing up, now the 1st and a foot or so lower in the water and has higher pressure than what the 2nd stage is exposed to. This may have been exacerbated by being fairly shallow at the time. I assume that things were workign similarly to how being shallow makes it harder to stay neutral because the air in your BC expands or compresses more when you change from 10' to 9' or 11' than it does when you change from 60' to 59' or 61'.

My regs are the Hollis DC3 1st and 212 2nd.

 

[tbone1004]

it has nothing to do with orientation of the stages, the first stage pumps out ambient plus nominal 135psi *depending on regulator and tuning, but either way it is plenty* 135psi is equivalent to 10ata give or take, so unless your lp hose is at 300ft and your first stage is at the surface, you'll be fine, rebreathers can get sensitive to orientation, but that has nothing to do with the stage orientation.

Traditional looking regulators have a diaphragm at the bottom when in normal diving configuration and the air inside the case is trying to create a vacuum as it escapes through the mouthpiece, this is why regulators freeflow if you set them in water diaphragm down, or if you take your mouth off of it without turning it mouthpiece down. When you are breathing regularly, you have the venturi assist helping you to push against the spring tension on the demand valve. When you are upside-down, you have the full tension of the demand valve, plus you are fighting to essentially suck a bubble back into your lungs, that's what makes it tough to breathe, it is the pressure differential between your lungs and the second stage, combined with not getting any assist from the venturi effect in the case.

 

[Akimbo]

Expanding tbone's explanation, think about the pressure you feel. You will find inhaling is a little easier and exhaling a little harder when the second stage is lower than your lungs (head-down). The pressure acting on the second stage’s diaphragm is several inches of water more than at the center-mass of your lungs. The second stage will try to inflate your lungs slightly to equalize the pressure.

Likewise, inhaling will be a little harder and exhaling a little easier when the second stage is higher than your lungs (head-up). The pressure is trying to squeeze your lungs. The inhalation and exhalation resistance will be about the same in the horizontal position because the second stage is very close to the same pressure gradient as the center-mass of your lungs.

This phenomenon is usually more noticeable with a double-hose regulator from the Cousteau and Sea Hunt days. You could take the mouthpiece out of your mouth and slowly raise it above the regulator behind you and it free-flowed. Lower it a little below and it stopped.

 

[scrane]

Having gone through a bunch of bad rental regulators in Roatan recently I finally broke down and bought an Atomic T2. It breathes dry and with equal pull in any orientation. It is great.

 

[halocline]

The wet breathing while inverted is due to water leaking in the exhaust valve as air escapes during exhalation; maybe a little around the mouthpiece, but the majority is in the exhaust valve. When you're in normal diving position, that water drains back out the exhaust valve, but when you're inverted, the mouthpiece flange is the de facto drain. Wet breathing 2nd stages usually have leaky exhaust valves. This is the one design flaw of the pilot/Air1; addressed in the later D series by using a smaller concentric exhaust valve instead of the diaphragm itself as the exhaust valve. Side exhaust regulators will breath wet just like any others, but only if the diver is positioned so the exhaust valve is pointing up and the mouthpiece flange is pointing down. Because these two points are not on opposite planes in the reg's case, a diver has to be kind of between on his side and on his back, with his head down a little, to sort of point the exhaust valve up and mouthpiece down. Plus, there are almost certainly differences in how well some exhaust valves seal water out.

As far as the added breathing resistance when looking up, it has to do with the 2nd stage geometry and the difference in depth between the mouthpiece the diaphragm/lever interface. This is also why a regulator will free-flow with mouthpiece up and not while pointing down. It has nothing to do with the relative depths of the 1st and 2nd stages, unless carried to extremes, like with a 20 foot hose so that IP would be compensating for a completely different depth. With doublehose regs, the 12" or so hoses between the mouthpiece and cans are carrying ambient pressure air, not air at IP. Hence, depth differences between the mouthpiece and cans are MUCH more sensitive.

 

[RJP]

I dive AquaLung Legend LX Supreme's for back gas. I can't MAKE them breathe wet under any conditions or orientation.

 

[Akimbo]

The wet breathing while inverted is due to water leaking in the exhaust valve as air escapes during exhalation; maybe a little around the mouthpiece, but the majority is in the exhaust valve...

I have not seen that except for some unusual exhaust valves that weren’t standard mushroom valves — few of which are made anymore. Anytime the exhaust valve leaked it was easily fixed by cleaning and replacing the mushroom.