Pressure rises after you stop breathing on reg.

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If you're seeing a 50-60 psi drop when you breathe a reg - I have to believe something is wrong - there is some limitation on the high pressure side.

Is there anything common? You say different tanks, sidemount so at least two regs - does it do it with both sets of regs? I have dual shearwater transmitors and there is no pressure drop that I see. Over time, yes, getting in and out of the water yes but never while in a constant state have I seen pressure drop other than a semi closed valve.
 
If you're seeing a 50-60 psi drop when you breathe a reg - I have to believe something is wrong - there is some limitation on the high pressure side.

Is there anything common? You say different tanks, sidemount so at least two regs - does it do it with both sets of regs? I have dual shearwater transmitors and there is no pressure drop that I see. Over time, yes, getting in and out of the water yes but never while in a constant state have I seen pressure drop other than a semi closed valve.

There are no sudden pressure drops, nor is the pressure rise sudden it is over a few minutes while I am breathing off the other reg. When I return to breathing off the reg there is a slow steady drop based off my breathing rate and depth.

And I see the behavior on both regs.
 
There are no sudden pressure drops, nor is the pressure rise sudden it is over a few minutes while I am breathing off the other reg. When I return to breathing off the reg there is a slow steady drop based off my breathing rate and depth.

And I see the behavior on both regs.

That's weird - next time I dive I'll look for that - I don't pay attention that close!!! Maybe your cave needs some fish or something to distract you LOL
 
That's weird - next time I dive I'll look for that - I don't pay attention that close!!! Maybe your cave needs some fish or something to distract you LOL

I don't typically notice it in the caves, unless it pushes up over the next 100 psi. I mostly notice it while looking at the dive profile after the fact.
 
Can you try different regs, first stage specifically? Leave everything else the same.
 
I don't typically notice it in the caves, unless it pushes up over the next 100 psi. I mostly notice it while looking at the dive profile after the fact.

What software are you using, my sidemount computer is sitting right here - curious if I see the same thing?
 
What software are you using, my sidemount computer is sitting right here - curious if I see the same thing?

Macdive and Shearwater Cloud.
 
Macdive and Shearwater Cloud.

I change tanks after 1st 1000 then run 2000 outa the second tank before switching and used Shearwater Cloud.

One dive: switched at 2020psi, psi drifted up to 2042, second tank changed at 914 and it drifted up to 922
Second dive: switched at 2006, drifted to 2022, second tank changed at 1034, drifted to 1042

Those were very long dives but the drift up happens within the first five minutes then stabilizes. The water temp here is 85. I use standard MK25 1st stages.

An idea - when you breathe in, there is a temperature drop of that gas as it enters the 1st stage, you breathe before you are swapping so that gas in the 1st stage is at it's coldest, now you stop the gas flow and the gas gradually heats up to ambient temp causing the slight rise in pressure.....

I think maybe that's what it is - the more or less could be different regs transferring heat better or worse, maybe even the volume of gas on the high pressure side of the regulator and probably somewhat the temperature of the surrounding water...

I think mystery solved!! LOL Hey, I updated my computers at least.
 
Can you try different regs, first stage specifically? Leave everything else the same.

I just checked, when I replaced one of my Deep 6s due to IP creep, with a Mk25/G250HP I see similar results.

An idea - when you breathe in, there is a temperature drop of that gas as it enters the 1st stage, you breathe before you are swapping so that gas in the 1st stage is at it's coldest, now you stop the gas flow and the gas gradually heats up to ambient temp causing the slight rise in pressure.....

I think maybe that's what it is - the more or less could be different regs transferring heat better or worse, maybe even the volume of gas on the high pressure side of the regulator and probably somewhat the temperature of the surrounding water...

I think mystery solved!! LOL Hey, I updated my computers at least.

Someone suggested something similar on the first page. Perhaps we are seeing the tank cooling due to the pressure drop, and it heats up while we are breathing off the other reg.

I'm just surprised that no one else noticed it before now.
 
I just checked, when I replaced one of my Deep 6s due to IP creep, with a Mk25/G250HP I see similar results.



Someone suggested something similar on the first page. Perhaps we are seeing the tank cooling due to the pressure drop, and it heats up while we are breathing off the other reg.

I'm just surprised that no one else noticed it before now.
Ok, seems to rule out one part of the puzzle so it’s likely somewhere in the other posts.
 

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