Older Sherwood first stage rubber plug?

[on_two_wheels]

I have an older Sherwood 1st stage with a rubber plug in it. The plug is hollow in the center. When I pull it out the hole it's in looks like a port minus the threads and no visible hole. Any idea what this might be for? Thanks.

 

[tbone1004]

A lot of the Sherwood regs have a positive pressure first stage and they blow a steady stream of bubbles out of the first stages. Kind of like an OPV I guess. Irritates the bejeezis out of me...

 

[herman]

That is an enviromental seal and while the small stream of bubbles irritates my diving sax playing buddy it is actually a very simple but effective system, one of the best IMO. On most flow by piston regs the ambient pressure (spring) chamber area is open to the water. Unless you flush it well it is an area of bad corrosion and for cold water diving it can be a source of freezing first stages. To seal the area, most manuf pack the area with grease or other goo, making a mess to clean up at service time and a pain in the rear to replace. Sherwood avoids this by placing a one way valve (the rubber plug) in the port of this chamber and purposely allowing (via an internal bypass port) a small amount of air to "leak" into the chamber and then exit the rubber port. This has the effect of equalizing the pressure in the chamber and at the same time keeping it dry. Sherwoods are known as the only reg that leaks on purpose but you will not find a better, simpler yet effective enviromental seal design on a piston reg. Put it back, pressurize it and hope you see a SMALL stream of bubbles coming out of the port. Sherwoods might irritate my buddy....which is not necessarly a bad thing but you will not find a more robust design.

 

[spectrum]

Herman described it well. I'll add that the air involved amounts to several breaths over the course of a dive, a non issue.

It's a good idea to mention this to a new buddy so they don't go berserk during the dive when they see your regulator "leaking".

If you don't have a small flow of bubbles several things may happen.
1) The check valve will leak and since you can't rinse the chamber it will corrode to heck.
2) The check valve will seal and on a deep dive ambient pressure will not be transferred to the chamber and the IP will not follow. Air delivery will suffer.
The slight airflow prevents each of these issues hence the bubble stream is not optional.

Pete

 

[on_two_wheels]

Thanks all. It's just a backup set of regs and will use it for rescue course. Just wanted to know before I got in the water. I appreciate the informative responses.

 

[tbone1004]

I just have a problem seeing my perfectly good regulator blowing bubbles on me...
I dove them this summer and the breathe real well, but my hearing is rather sensitive, and that's how I can tell when people are trying to sneak up on me and the bubbles inhibit that... I realize it's for a good reason, and it helps, especially in salt, but I'll stick to my balanced diaphragm's thank you very much :-D with no leakage

 

[spectrum]

Wear a hood, no more problem.

Do you have a lot of divers sneaking up on you?

 

[Luis H]

Wear a hood, no more problem.

Do you have a lot of divers sneaking up on you?

It happens... I see it on "Sea Hunt" all the time.

 

[tbone1004]

when doing open water training we sneak up on the divers, and subsequently my boss sneaks up on us to make sure we're babysitting properly. I can usually hear him trying to be sneaky and will look around and make faces. The bleed is just a nuisance in that bad.