Positive test only. What are the down sides?

Mark Chase · 13th October 2006, 13:26

OK so my unit will not hold negative due to the V4tec BOV design that cant isolate the mouthpiece from the loop in a gas tight manor. (I am told this is not a problem in use)

Sooooooo what are the down sides with only doing a positive test if you spray all the joints with liquid soap and water?

When my unit fails Neg i find the leek with liquid soap and water so why not just cut out the middle man and go streight for the positive test?

Any thing i have missed?

ATB

Mark Chase

viscya · 13th October 2006, 13:30

If closing the DSV (switch to BOV) does not seal tight, won't water leak in when you take the mouthpiece out under water?

Mark Chase · 13th October 2006, 13:31

Quote: (Originally Posted by viscya)

If closing the DSV (switch to BOV) does not seal tight, won't water leak in when you take the mouthpiece out under water?

I am told no, but ill let you know after i have had a go. Water is after all some what thicker than air.

ATB

Mark Chase

divetheworld · 13th October 2006, 13:36

Quote: (Originally Posted by Mark Chase)

OK so my unit will not hold negative due to the V4tec BOV design that cant isolate the mouthpiece from the loop in a gas tight manor. (I am told this is not a problem in use)

Sooooooo what are the down sides with only doing a positive test if you spray all the joints with liquid soap and water?

When my unit fails Neg i find the leek with liquid soap and water so why not just cut out the middle man and go streight for the positive test?

Any thing i have missed?

ATB

Mark Chase

Hyperthetically speaking, you could have a small puncture or dislodged 'o' ring that acts as a one way valve due to the way it is damaged/sat.
This would be a rare occurrence to say the least, and without sticking my head above the trenches too much I would say that it would be personal risk-assessment as to how far you would go.
IMHO it is very unlikely that there would be a problem that would be missed, but, thats not to say there could not be one.
With a Bob Howell, I close the BOV and use the Dil add button to pressurise for a pos test, you cant do it by mouth as switching the BOV to bail lets the pressure out the exhaust valve.
For the neg test, I close the gas supply to the BOV with the flow stop and vac it down in my mouth.
Job done.
Sometimes I get some slight seepage out of the 'o' rings when at the very top end of the pos test but I'm happy with that.

Brent

KevDD · 13th October 2006, 15:53

I've been diving my ccr for about 6 months now and until last night my unit wouldn't hold a neg for more than a few minutes. I gave it a good service and its grand now. Must have been an accumulation of dirt on orings.

Failed neg but usually passed the positive test.

E-man · 14th October 2006, 20:00

I've found all my leaks via positve tests, if you can submerse the whole unit and get a decent positive pressure thats the best, but usually not too practical to do. Also i've found that crysto lube, electrical tape, and tie-wraps can fix almost any leak you have.

tecdivertraining · 15th October 2006, 01:52

Quote: (Originally Posted by Mark Chase)

OK so my unit will not hold negative due to the V4tec BOV design that cant isolate the mouthpiece from the loop in a gas tight manor. (I am told this is not a problem in use)

Sooooooo what are the down sides with only doing a positive test if you spray all the joints with liquid soap and water?

When my unit fails Neg i find the leek with liquid soap and water so why not just cut out the middle man and go streight for the positive test?

Any thing i have missed?

ATB

Mark Chase

Mark

If you had a problem with the manual inflators then I guess you would not spot if they were leaking o2 or dill into the loop on the positive test as the leak could be small and would pass a soap/water check. I would say the same for the ADV but I guess you can check these later by pressurizing and turning off the tanks to ensure pressure is maintained, I do this as part of pre-dive checks anyway.

Cheers

Mark Chase · 15th October 2006, 15:41

Quote: (Originally Posted by tecdivertraining)

Mark

If you had a problem with the manual inflators then I guess you would not spot if they were leaking o2 or dill into the loop on the positive test as the leak could be small and would pass a soap/water check. I would say the same for the ADV but I guess you can check these later by pressurizing and turning off the tanks to ensure pressure is maintained, I do this as part of pre-dive checks anyway.

Cheers

Interesting i definitly hadent thaught of this one.

ATB

Mark Chase

DaveC · 16th October 2006, 01:52

Quote: (Originally Posted by tecdivertraining)

Mark

If you had a problem with the manual inflators

Cheers

I actually had a small issue with the inflator on my BC. It wasn't holding the pressure or something and when doing a neg test, this is where it was pulling the gas in threw. Also, the o-ring on the DIL valve wasn't seeting correctly and a neg test pull this out as well. Possitive presure will only find somethings, but not all.

13th October 2006, 13:26	#1 (permalink)
Mark Chase RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,821	Positive test only. What are the down sides? OK so my unit will not hold negative due to the V4tec BOV design that cant isolate the mouthpiece from the loop in a gas tight manor. (I am told this is not a problem in use) Sooooooo what are the down sides with only doing a positive test if you spray all the joints with liquid soap and water? When my unit fails Neg i find the leek with liquid soap and water so why not just cut out the middle man and go streight for the positive test? Any thing i have missed? ATB Mark Chase __________________ See my "Doing It Chasey" video where I'm locked into a padded room, naked, with two ball bearings and within an Hour, I manage to lose one and break the other!!! Kevin Juergensen 16/11/08 [/quote]
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13th October 2006, 13:30	#2 (permalink)
viscya Wrecking Crew Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Oct 2005 Location: Marlton New Jersey Posts: 138	Re: Positive test only. What are the down sides? If closing the DSV (switch to BOV) does not seal tight, won't water leak in when you take the mouthpiece out under water? __________________ "There is nothing majestic or dignified about being left to silently rot and collapse under heaps of old fishing net forgotten and unappreciated in dark and unvisited waters." DrMike
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13th October 2006, 13:31	#3 (permalink)
Mark Chase RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,821	Re: Positive test only. What are the down sides? Quote: (Originally Posted by viscya) If closing the DSV (switch to BOV) does not seal tight, won't water leak in when you take the mouthpiece out under water? I am told no, but ill let you know after i have had a go. Water is after all some what thicker than air. ATB Mark Chase __________________ See my "Doing It Chasey" video where I'm locked into a padded room, naked, with two ball bearings and within an Hour, I manage to lose one and break the other!!! Kevin Juergensen 16/11/08 [/quote]
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13th October 2006, 13:36	#4 (permalink)
divetheworld Dive porn pimp Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Classic Kiss Other CCR Join Date: Mar 2005 Location: Leeds, England Posts: 1,630	Re: Positive test only. What are the down sides? Quote: (Originally Posted by Mark Chase) OK so my unit will not hold negative due to the V4tec BOV design that cant isolate the mouthpiece from the loop in a gas tight manor. (I am told this is not a problem in use) Sooooooo what are the down sides with only doing a positive test if you spray all the joints with liquid soap and water? When my unit fails Neg i find the leek with liquid soap and water so why not just cut out the middle man and go streight for the positive test? Any thing i have missed? ATB Mark Chase Hyperthetically speaking, you could have a small puncture or dislodged 'o' ring that acts as a one way valve due to the way it is damaged/sat. This would be a rare occurrence to say the least, and without sticking my head above the trenches too much I would say that it would be personal risk-assessment as to how far you would go. IMHO it is very unlikely that there would be a problem that would be missed, but, thats not to say there could not be one. With a Bob Howell, I close the BOV and use the Dil add button to pressurise for a pos test, you cant do it by mouth as switching the BOV to bail lets the pressure out the exhaust valve. For the neg test, I close the gas supply to the BOV with the flow stop and vac it down in my mouth. Job done. Sometimes I get some slight seepage out of the 'o' rings when at the very top end of the pos test but I'm happy with that. Brent __________________ Attitude and self praise is no reccomendation. Dont try to be a great man, just be a man and let history be the judge of you. *WWW.NARKEDAT90.CO.UK* *http://www.grpservices.com/pursuit/* Supporting Shearwater Research Products in Europe
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13th October 2006, 15:53	#5 (permalink)
KevDD Custom Title Allowed! Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Oct 2005 Location: Dublin, Ireland Posts: 99	Re: Positive test only. What are the down sides? I've been diving my ccr for about 6 months now and until last night my unit wouldn't hold a neg for more than a few minutes. I gave it a good service and its grand now. Must have been an accumulation of dirt on orings. Failed neg but usually passed the positive test.
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14th October 2006, 20:00	#6 (permalink)
E-man On the loop! Current Rebreather/s: Inspiration Classic Optima Other Rebreather/s: Titan Join Date: Sep 2005 Location: Eastern Coast ;) Posts: 212	Re: Positive test only. What are the down sides? I've found all my leaks via positve tests, if you can submerse the whole unit and get a decent positive pressure thats the best, but usually not too practical to do. Also i've found that crysto lube, electrical tape, and tie-wraps can fix almost any leak you have.
(Offline)

15th October 2006, 01:52	#7 (permalink)
tecdivertraining RebreatherWorld Sponsor Current Rebreather/s: Inspiration Classic Inspiration Vision Evolution Megalodon Ouroboros Dolphin Other Rebreather/s: Not Bought Yet Dolphin Join Date: May 2005 Location: Phuket, Thailand Posts: 514	Re: Positive test only. What are the down sides? Quote: (Originally Posted by Mark Chase) OK so my unit will not hold negative due to the V4tec BOV design that cant isolate the mouthpiece from the loop in a gas tight manor. (I am told this is not a problem in use) Sooooooo what are the down sides with only doing a positive test if you spray all the joints with liquid soap and water? When my unit fails Neg i find the leek with liquid soap and water so why not just cut out the middle man and go streight for the positive test? Any thing i have missed? ATB Mark Chase Mark If you had a problem with the manual inflators then I guess you would not spot if they were leaking o2 or dill into the loop on the positive test as the leak could be small and would pass a soap/water check. I would say the same for the ADV but I guess you can check these later by pressurizing and turning off the tanks to ensure pressure is maintained, I do this as part of pre-dive checks anyway. Cheers __________________ Mathew Partridge Technical Director Pro-Tech Dive College www.protechdivers.com www.tech-ccr.com
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15th October 2006, 15:41	#8 (permalink)
Mark Chase RBW Member Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,821	Re: Positive test only. What are the down sides? Quote: (Originally Posted by tecdivertraining) Mark If you had a problem with the manual inflators then I guess you would not spot if they were leaking o2 or dill into the loop on the positive test as the leak could be small and would pass a soap/water check. I would say the same for the ADV but I guess you can check these later by pressurizing and turning off the tanks to ensure pressure is maintained, I do this as part of pre-dive checks anyway. Cheers Interesting i definitly hadent thaught of this one. ATB Mark Chase __________________ See my "Doing It Chasey" video where I'm locked into a padded room, naked, with two ball bearings and within an Hour, I manage to lose one and break the other!!! Kevin Juergensen 16/11/08 [/quote]
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16th October 2006, 01:52	#9 (permalink)
DaveC New Member Current Rebreather/s: Sport Kiss Classic Kiss Other Rebreather/s: Prism Topaz Join Date: Mar 2005 Location: Ontario. Canada Posts: 192	Re: Positive test only. What are the down sides? Quote: (Originally Posted by tecdivertraining) Mark If you had a problem with the manual inflators Cheers I actually had a small issue with the inflator on my BC. It wasn't holding the pressure or something and when doing a neg test, this is where it was pulling the gas in threw. Also, the o-ring on the DIL valve wasn't seeting correctly and a neg test pull this out as well. Possitive presure will only find somethings, but not all. __________________ Dave Any day in the water is better then any day in the office.
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