Could someone explain the differences between the balanced and unbalanced p-valves, how they actually work and pros and cons of each? I will be getting one soon and don't know enough about them to decide which one to get. Thanks.
Workings of a P-Valve
- Thread starter thmoose51
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DIR-Atlanta
Contributor
A balanced P-valve has a couple of check valves in it to allow gas from inside the drysuit to automatically equalize the air space in the tubing, while ensuring that any discharged fluid goes out of the suit. If this air space is not equalized, then it is subject to the same issues of compression as any air space, which could result in a very unpleasant squeeze (on a part of your anatomy where you'd probably rather not have one).
With an unbalanced P-valve, you can mitigate this problem by doing a (ahem) "P-drill" at the beginning of each dive, to make sure that any air in the tubing is displaced by liquid. Just opening the external discharge port will not accomplish this, since the air space will just be compressed back into the tubing (or someplace worse!).
My first P-valve was the unbalanced variety, which worked fine for most of the depths I was diving at the time (recreational profiles only). As you get into deeper diving, a balanced P-valve becomes more desirable (almost a necessity), and I personally would not even bother with an unbalanced one nowadays, for any of the diving I do.
Please explain this. Mine is unbalanced, I never have any squeeze, I never leak, and don't have any other problems. I hear of tons of people with balanced systems that have difficulty doing the deed and with leaks. Granted I don't do the depths that you do. Maybe this is a stupid question - please forgive my ignorance if it is - but as long as the system is primed before descent then what does it matter if you are at 60 ft or 250 ft. Thanks
Hunter
Peter_C
Contributor
My balanced p-valve leaked sea water and it was always hard to pee, and I had to pee really slow. Now that I replaced it with an unbalanced I find it easy to cut loose and pee and not a single leak has happened. I do not do deco dives, but not sure that really changes anything other than maybe opening the bolt for a second around a mid water deco stop?
Use an unbalanced p-valve a lot - definitely no problems at all with depth or squeeze - I mostly just leave it open all the time (most - all?- have a safety bolt in the valve opening so you can close it off if you aren't using it or something starts leaking). As the valve is open all dive, water can get in and out equalizing pressure and keeping it clean - and without valves it is easier to clean after the dive and there is less to go wrong. Have done ice diving and don't find cold water (coming in the open valve) a problem either. Unbalanced p-valve is IMHO highly recommended.
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