212 Purge sticking?

sdahl38 · Oct 13, 2010

I bought a DC2/212 set for my wife from LP a few months ago and just finally had a chance to try it with her in a pool session with one of our LDS. With the Venturi switch in the dive position when we pushed the purge button to check for proper air flow from tank the purge button would appear to get stuck and basically free flow. The only way to prevent this from happening was to put the Venturi switch to the pre-dive position. What am I missing? Do I just need to adust the Dynamic Adjustment Knob to prevent this?

CT Sean · Oct 13, 2010

Are you above or below the surface? My understanding is that it was normal for a reg to free flow when purged in open air in this situation. This is the point of the "pre-dive" switch

sdahl38 · Oct 13, 2010

CT Sean, this is above the water. My Scubapro MK25/G250 does not free flow when you purge above the water???? I thought the point of pre-dive switch was to prevent free flow if the reg were upside down in the water before you put in your mouth.

CT Sean · Oct 13, 2010

Both my wife's an my Oceanic regs (which are nearly the same as Hollis) will free flow on the surface with the venturi switch "open". Always assumed this was expected.

I found this regarding this topic:

http://www.scubaboard.com/forums/regulators/304770-dive-predive-adjustment.html

Post #5 explains it pretty well.

For the record, my adjustment knob is usually wide open before a dive as that is how I store it so it stands to reason my reg would free flow with the venturi in the + position.

Hollis Gear Nick · Oct 13, 2010

sdahl38:
I bought a DC2/212 set for my wife from LP a few months ago and just finally had a chance to try it with her in a pool session with one of our LDS. With the Venturi switch in the dive position when we pushed the purge button to check for proper air flow from tank the purge button would appear to get stuck and basically free flow. The only way to prevent this from happening was to put the Venturi switch to the pre-dive position. What am I missing? Do I just need to adust the Dynamic Adjustment Knob to prevent this?

[FONT=&quot]
[/FONT]Hi Sdahl38,

Thanks for the post and question. The 212 is a high performance regulator, and as such it is recommended that an adjustment be made to either the Venturi switch or to the adjustment knob (or a combination of both) if the regulator is going to be out of the divers mouth for an extended time. The work of breathing on the 212 is so low that without the backpressure generated by the diver's mouth/airway a slight amount pressure on the diaphragm could cause the venture assist to overpower the poppet spring and allow the regulator to free flow. While this will not happen when the regulator is in the divers mouth, it is easily prevented on the surface by either setting the venture switch to the pre-dive setting, or turning the cracking pressure adjustment knob clockwise about 1 ½ turns. The 212 is a balanced second stage, so once it is set at the surface the performance and work of breathing will remain constant through out the dive.

Hope this helps,

sdahl38 · Oct 13, 2010

Nick, thanks for your reply. I stopped by one of the LDS here in Vancouver today that you had recommended to me a while ago and they basically told me the same thing. Thanks again.

skankpile · Oct 13, 2010

Apeks do the same and its actually a final test procedure in their maintenance manual (Maintenance Manual for Authorized Technicians, Issue 4 23/11/2006) for the XTX regs.

I'll do it after I rinse them and just hold my thumb over the mouth piece or turn the venturi back towards the diaphragm and it will stop. Its also a great cat repellent.

212 Purge sticking?

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