Changing regs (1st stages) underwater?

[vicky]

Is it possible to change first stages underwater? (Suppose there is no other option but to do it- deco reg fails, and a recompression chamber is several hours away- there is no other divers/support to get you a spare tank+reg and your buddy is short on air Wow, nobody would dive in these conditions perhaps, but it is only a theorethical question).

Is there any difference if salt or sweet water penetrates thorugh the first stage? Would you keep diving after such an incident, or abort any plans and send the reg to service ASAP?

 

[Diver0001]

vicky once bubbled...
Is it possible to change first stages underwater? (Suppose there is no other option but to do it- deco reg fails, and a recompression chamber is several hours away- there is no other divers/support to get you a spare tank+reg and your buddy is short on air Wow, nobody would dive in these conditions perhaps, but it is only a theorethical question).

Is there any difference if salt or sweet water penetrates thorugh the first stage? Would you keep diving after such an incident, or abort any plans and send the reg to service ASAP?

Yes In an emergency it's an option. Water in the 1st stage usually means getting it serviced. Apart from the salt/sweet thing water usually has some particulates in it that can clog the filter and so forth.

R..

 

[Campana]

I wouldn't worry too much about first and second stages. You could just take them apart and clean them. I do worry that water would get into your high pressure hose and be driven into your spg. If you ever do this, be sure to remove the spg and clean the hose. I've never taken an spg apart, and wonder how difficult it would be.

 

[jonnythan]

Campana once bubbled...
I wouldn't worry too much about first and second stages. You could just take them apart and clean them. I do worry that water would get into your high pressure hose and be driven into your spg. If you ever do this, be sure to remove the spg and clean the hose. I've never taken an spg apart, and wonder how difficult it would be.

Tried it once. Not sure how it happened, but some water backed up into the SPG housing during a pool dive.

The SPG was plastic backing and acrylic face glued together - no way to take it apart and check it out. So I did what any reasonable male would do. I bought another one and took a hammer to the old one.

Thing was tough as hell.. took me a solid 5 minutes with the hammer and a concrete porch to crack the thing open.

The pressure gauge (at least in this SPG) was a long coil of what appeared to be 1/8" thin gauge copper strip. Uncoiled it probably would have been 6 or 7 feet long. The needle was attached to the end of it (in the center).

Upon further proving my manhood and cracking the copper-looking strip, I noticed a tiny hole going through the center of it. Then I realized that the copper strip was actually a tube with a very very small internal diameter. It fills with pressurized air and expands a little, causing the needle to turn.

I'm not sure if all SPG's are exactly like this one, but if any water gets into it - internals or just the housing - it's done for. The chance of some corrosion in the housing making the needle stick, and the effects of having moisture inside the 6 feet of copper tubing, is just not worth saving $75. Get a new SPG if you pull this maneuver.

 

[FredT]

I spent a week of long days underwater excaving a sensor cable run in coral rubble by hand in about 10'. (8-10 tanks a day/national park with anal Ranger so power wasn't an option) My ears took exception to this and started to give me trouble during equalizing for tank changes, so I had a tender drop me bottles on a line to eliminate most of the bouncing. I didn't have a spare reg, so when one tank started breathing hard I'd go over to the one on the bottom and swap out the reg and pack, then yank the buoy line so they'd pull up the dead one send down aother full one.

About every other day I'd pull the reg down, rinse it in fresh water and hang new o-rings in it. No problems and my ears dien't get any worse.

BTW the night before we finished the installation a strom moved through and scoured all the live coral off the rubble the Ranger was so anal about protecting. The last dive was done on bare limestone/coral rubble, so the hand excavation was totally wasted effort. I got my finger prints back after a couple weeks.

FT

 

[vicky]

However, I think that the hole diameter in the HP tube that goes into the SPG is so small, that I wonder if any water is going to sip through it. Do you know what is the diameter of the HP port (the one that goes to the SPG). I think in my reg is is a pinhole, barely distinguishable with the naked eye..
Did you find any water traces in the SPG that you hammered?

 

[jonnythan]

vicky once bubbled...
However, I think that the hole diameter in the HP tube that goes into the SPG is so small, that I wonder if any water is going to sip through it. Do you know what is the diameter of the HP port (the one that goes to the SPG). I think in my reg is is a pinhole, barely distinguishable with the naked eye..
Did you find any water traces in the SPG that you hammered?

There was a leak in the housing somewhere, not the first stage or the hose. The water didn't enter the pressurized part.

In any case, I think that if you have water in the first stage then put 3000 psi behind it, water will get into the pressurized portion of the SPG.

After all, with a hole that small in diameter.. if there's any water *in* the system and you put all that air behind it... where else can the water go? Submerged first stage tank switch = new SPG.

 

[The Chairman]

of an SPG should in no way hurt it or affect it's movement/accuracy. That is my honest unequivocal opinion based on personal observations and long arduous years of speculation. Anyone with actual facts to the contrary is obviously just itching for a fight and would be wise to watch what they post! :tease:

 

[vicky]

jonnythan once bubbled...


There was a leak in the housing somewhere, not the first stage or the hose. The water didn't enter the pressurized part.

In any case, I think that if you have water in the first stage then put 3000 psi behind it, water will get into the pressurized portion of the SPG.

After all, with a hole that small in diameter.. if there's any water *in* the system and you put all that air behind it... where else can the water go? Submerged first stage tank switch = new SPG.

If you have some failure while the reg is attached to the bottle (and under pressure) then most probably you'll have bubbles coming out through the "leak source". As long as you don't turn off the bottle and depressurise, you'll have a constant stream of small (or big??) bubbles, and indeed it is quite common to see bottles with a bad o-ring and you see bubbling coming out from there.

However, when you want to change the regs underwater one *has* to turn off the bottle and relieve pressure in order to open the first stage. Now there is ambient pressure in the entrance to the first stage (water), and ambient pressure in the SPG hose (air?). I guess NetDoc is right about this issue and no water sips in through the pinhole (and I understand he is one of the forum's bosses, so why should I contradict him? :tease: )

Anyway, I think I learned something today, so thanks to you all!

 

[The Chairman]

I was trying to make the point (in my offhanded humorous sort of way), that it was merely my opinion about the SPG... not a proven fact that I was espousing. Please feel free to disagree with me anytime.

As for changing out the first stage... that's more than I would care to do on any particular dive. I really can't think of a situation where I would think otherwise. If I had a problem with one first stage, I would crank that knob off and use my other one (I do use two, with either an H-valve or doubles).