AL 40 Stage Bottle leaks when under water. Pressure drops

[Peter69_56]

I was taught to open and close the valve on an otherwise closed deco cylinder now and again on a dive to avoid water getting back past the second stage.

I do the same as a matter of course. You never know if you have bumped the face of the reg, or if it has free flowed a little. open and close the valve a few times during the dive, as an automatic reaction, thus ensuring the reg has gas in it and not water.

 

[Imla]

Just to be clear. You open the valve. You read the pressure. You then close the valve. Pressure reads the same. Then, after a while in the water you have lost a little bit of pressure when you are checking your spg? You still haven't opened the valve again?

It is quite normal to lose a bit of pressure. THere is not much gas in the hose. You could have bumped the 2nd stage against something and let the gas out. The water is colder, so the gas could have compressed a bit. But, I'll but my $0.02 on the "purging" solution.

Solution: open valve. Check pressure to be ok. Close valve again. (Of course, if this repeats, check placement of 2nd stage. If still not better, check 2nd stage when you get on land)

 

[NAM001]

Ken if you guess is corrrect then we all have this problem,. This guy needs to turn it on and leave it on and watch for declining psi.

 

[Peter69_56]

Just to be clear. You open the valve. You read the pressure. You then close the valve. Pressure reads the same. Then, after a while in the water you have lost a little bit of pressure when you are checking your spg? You still haven't opened the valve again?

It is quite normal to lose a bit of pressure. THere is not much gas in the hose. You could have bumped the 2nd stage against something and let the gas out. The water is colder, so the gas could have compressed a bit. But, I'll but my $0.02 on the "purging" solution.

Solution: open valve. Check pressure to be ok. Close valve again. (Of course, if this repeats, check placement of 2nd stage. If still not better, check 2nd stage when you get on land)

If its just cold water, you will not see any gas leak. If its a leak, you should see it, it might be a small leak but it will show a trail of bubbles, after all the bubbles don't just magically disappear. So if you check all the components closely in the water, swivel the secondary reg etc and move the hoses if you see no bubbles then there is no leak. Thus cold or bumping the secondary reg face making it dump a little gas?

I think tracking down the fault will be easy

 

[Stoo]

You have a small leak either on the 1st stage or second stage or gauge. Simply put it under the water turned on and see where the air leaks from.

The OP mentioned that he turns the tank off, so a leak in the reg wouldn't account for it..

Drop in water temp will certainly account for some loss, especially if you have gone from a hot fill to a cold dive in short order.

If this doesn't account for it, you could have a small leak in the valve stem o-rings or possibly around the burst disk.

 

[Peter69_56]

The OP mentioned that he turns the tank off, so a leak in the reg wouldn't account for it..

Drop in water temp will certainly account for some loss, especially if you have gone from a hot fill to a cold dive in short order.

If this doesn't account for it, you could have a small leak in the valve stem o-rings or possibly around the burst disk.

Yep I agree, and either the leak shows in the water and its a real leak, or it doesn't thus its just cooling or bumping the second stage diaphragm. The solution to this problem seems easy to find.

 

[scubadude223]

I pressurize the Stage Bottle at the Start of the Dive. I have around 2700 PSI in the tank.
This is because I dive a lot with it, so I don't top it off every dive. I pressurize it at the surface and turn it off after I pressurize it. When I'm diving with it, I have the hose fully charged but the bottle off.

I check it during the dive. Every once in a while or so I have to add air by opening and closing it. This is not a big deal, the air loss is very small and does not cause any real problem.

Could the act of swimming with it cause this?
Do the guys here that have Stage Bottles have the same issue

thanks for the help

 

[Searcaigh]

I frequently open and close the valve on my stage bottle, it is easy to slightly purge it without noticing especially when taking photographs.

I sometimes notice a slight drop registering on the SPG hence the habit of opening and closing the valve during the dive.

 

[RJP]

I have never seen the pressure on a pressurized reg/closed tank NOT drop during the course of a dive. If it was a meaningful leak... you'd notice it. You'd hear it or see it.

Given how small a volume of gas is in the hose to begin with, a 500psi drop is not a lot of gais.

An easy test is to pressurize it and close tank valve AT HOME and see what happens over what period of time when it's not being jostled around. If you want to go nuts... spray it with some soapy water.

 

[dumpsterDiver]

The OP mentioned that he turns the tank off, so a leak in the reg wouldn't account for it..

Drop in water temp will certainly account for some loss, especially if you have gone from a hot fill to a cold dive in short order.

If this doesn't account for it, you could have a small leak in the valve stem o-rings or possibly around the burst disk.

No you are completely wrong.. If he turn the tank valve off, then the stem o-ring has nothing to do with it. if he turns the valve off, then the leak has nothing to do with a burst disk. If he turns the valve off, then it IS associated with the regulator or the valve/regulator interface o-ring.