Regulator Repair or Replace? That is the Question.

[rsingler]

What the hell is IP instability and how do I check for it?

In order to breathe from a tank containing 3000 psi, you need some sort of a valve. You could use the tank valve, cracking it and taking a breath if you carried it in your arms, but that is a little cumbersome, lol.
From the very earliest days, designers discovered that dropping from tank pressure (3000psi) to inhalation pressure (-0.035 PSI) was simply too big of a gradient for a valve to operate smoothly.
So they engineered a way to make the pressure changes in two steps, or stages. The first stage takes tank pressure from 3000 PSI to a constant 150 psi (or so). The second stage takes 150 psi and reduces it to zero with a valve that opens at -.035 PSI. The pressure changes of those two jumps are easy enough for engineers to make smooth.
The 150 psi of the first stage is the Intermediate Pressure. The magic of the first stage, as opposed to a welding regulator, is that it maintains that IP as you descend in an environment that has increasing pressure with depth (seawater). For example, at 99 feet , where seawater ambient pressure is 45 PSI, the first stage delivers 195 PSI. After you subtract out the 45 PSI that you are swimming in, the first stage output is magically 150 psi.
The first and the second stage are tuned together. That means that each piece produces the output expected by the other. For example, as the regulator checklist will remind you, if the first stage is leaking inside and IP begins to increase, at a certain point it will be too much for the second stage to handle, which will then begin to freeflow.
Therefore, a very easy check for a diver to learn is how to connect a $20 pressure gauge to his LPI inflator connection before he connects it to his bcd. With that gauge in place, a few quick purges of the second stage will show the IP dropping the correct amount as the second stage flows, then briskly popping back to the designed IP . From there it should not change at all. That 5-20 second check reassures you that your first stage is ready for your dive. A slightly longer version of that test where you leave a tank connected overnight, coming back the next morning to find the IP right where it should be, confirms that your first stage needs no service.
Go try out @couv 's Regulator Checklist . It's cool!

 

[rsingler]

the reg tech told me that there was corrosion in the 1st stage. I was blown away by that.

For a diaphragm first stage reg like your Aqualung, the only part of the reg that should be exposed to sea water corrosion is the outside. Now if the model doesn't have an environmental seal, the "outside" also includes the main spring and outside surface of the diaphragm. But "corrosion" there is pretty meaningless verdigris.
On the other hand, there is an easy way for corrosion to get inside your first stage: tank changes.
When you finish boat dive #1, the Divemaster may race along the boat, slipping the gear off one tank and onto the next. The cap NEVER gets placed on the first stage during the change. A little drop of sea water from the wet gear, that falls on the sintered metal filter where the first stage meets the tank, then gets blown inside the mechanism when the rig is pressurized. Do that a few dozen times on a few boat trips, and let your first stage sit in your closet in between trips, and you have "corrosion in your first stage."

Nobody but me changes my tank. I'm polite, and the DM's usually don't get huffy about it. If I'm on a boat where the tanks are refilled from a central large tank during the Surface Interval, I'm religious about removing my first stage, drying the sealing area, and recapping the air opening while it's lying wet on my bcc.

 

[unwantedsn]

This is a good video about IP from Alec Peirce. Shows you how to check, and make your own IP gauge if you want to go the DIY route.

 

[grf88]

Maybe another question is inspect or service. Many regs get serviced much more frequently than required and many regs have problems immediately after service. Why not learn to inspect them yourself to determine if service is really necessary. There is some great information in this thread:
Regulator checklist and inspection

 

[runsongas]

Never knew that my reg had free parts for life. I don't think it does. But even if it does, okay. That covers about $10 of the repair. I usually service the reg every couple of years, but I had it serviced last year and in my shop this year because I was running into problems with a free-flow. We figured out that the swivel I recently put on it was probably causing the free-flow. The LDS does not do the repairs, they send the unit out. Their tech came by to drop off some regs he was working on and looked at mine. He found the pressure parameters all out of whack and suggested a service. I definitely don't want a jacked-up reg, and since I'm diving next week (Whale sharks and sea lions in La Paz, MX ), I thought it best to get it done.

free parts covers more like 50 to 80 dollars of a dealer overhaul. about 40 dollars for the first stage and 20 each for the second stages. if you were not charged for parts, the labor charge is double what i would expect. but if you had skipped a previous service, that would explain why the bill is significantly higher.

 

[Jay Moroso]

My solution after getting a $300.+ bill for 3 regulator overhauls was to learn to service them myself. Now for less than $100.00 in parts and a one time cost of a $200.00 for tools and equipment I overhaul my regs myself. Even overhauled my old double hose reg. Using new materials like silicone instead of the old rubber parts it breathes easier than it ever did. Regulators are VERY simple devices and are very easy to work on with the right tools and a little reading. My only regret was not starting to do my own years ago.

Where did you learn this?

 

[johndiver999]

For a diaphragm first stage reg like your Aqualung, the only part of the reg that should be exposed to sea water corrosion is the outside. Now if the model doesn't have an environmental seal, the "outside" also includes the main spring and outside surface of the diaphragm. But "corrosion" there is pretty meaningless verdigris.
On the other hand, there is an easy way for corrosion to get inside your first stage: tank changes.
When you finish boat dive #1, the Divemaster may race along the boat, slipping the gear off one tank and onto the next. The cap NEVER gets placed on the first stage during the change. A little drop of sea water from the wet gear, that falls on the sintered metal filter where the first stage meets the tank, then gets blown inside the mechanism when the rig is pressurized. Do that a few dozen times on a few boat trips, and let your first stage sit in your closet in between trips, and you have "corrosion in your first stage."

Nobody but me changes my tank. I'm polite, and the DM's usually don't get huffy about it. If I'm on a boat where the tanks are refilled from a central large tank during the Surface Interval, I'm religious about removing my first stage, drying the sealing area, and recapping the air opening while it's lying wet on my bcc.

I think you forgot to mention an even more common means to introduce seawater into a first stage (on small boats anyway).
When it is rough, seawater splashes the tanks and very often finds its way into the valve. It is very beneficial to crack the valve and blow out any water before connecting the reg or filling the tank

 

[Jay Moroso]

Like Marie I believed my Aqualung Legend was superior to most regs. Now that I have serviced a few differently models/brands I no longer think that and sold it. My “POS” hog regs look to be made of similar quality/ breathe as well when tuned and and a second stage costs $13 to service. The inhalation effort adjuster on the legend second is a poor design, gets stiff even with thorough washing.

Hmmmm....Something to think about...Thanks.

 

[uncfnp]

Where did you learn this?

For me...

Scubaboard DIY forum
SCUBA REGULATOR MAINTENANCE AND REPAIR by Vance Harlow
Regulator Savvy Book | Scuba Tools

 

[Jay Moroso]

In order to breathe from a tank containing 3000 psi, you need some sort of a valve. You could use the tank valve, cracking it and taking a breath if you carried it in your arms, but that is a little cumbersome, lol.
From the very earliest days, designers discovered that dropping from tank pressure (3000psi) to inhalation pressure (-0.035 PSI) was simply too big of a gradient for a valve to operate smoothly.
So they engineered a way to make the pressure changes in two steps, or stages. The first stage takes tank pressure from 3000 PSI to a constant 150 psi (or so). The second stage takes 150 psi and reduces it to zero with a valve that opens at -.035 PSI. The pressure changes of those two jumps are easy enough for engineers to make smooth.
The 150 psi of the first stage is the Intermediate Pressure. The magic of the first stage, as opposed to a welding regulator, is that it maintains that IP as you descend in an environment that has increasing pressure with depth (seawater). For example, at 99 feet , where seawater ambient pressure is 45 PSI, the first stage delivers 195 PSI. After you subtract out the 45 PSI that you are swimming in, the first stage output is magically 150 psi.
The first and the second stage are tuned together. That means that each piece produces the output expected by the other. For example, as the regulator checklist will remind you, if the first stage is leaking inside and IP begins to increase, at a certain point it will be too much for the second stage to handle, which will then begin to freeflow.
Therefore, a very easy check for a diver to learn is how to connect a $20 pressure gauge to his LPI inflator connection before he connects it to his PC. With that gauge in place, a few quick purges of the second stage will show the IP dropping the correct amount as the second stage flows, then briskly popping back to the designed IP . From there it should not change at all. That 5-20 second check reassures you that your first stage is ready for your dive. A slightly longer version of that test where you leave a tank connected overnight, coming back the next morning to find the IP right where it should be, confirms that your first stage needs no service.
Go try out @couv 's Regulator Checklist . It's cool!

AWESOME explanation. I never knew all of that. Thank you for taking the time to post this. You have

For a diaphragm first stage reg like your Aqualung, the only part of the reg that should be exposed to sea water corrosion is the outside. Now if the model doesn't have an environmental seal, the "outside" also includes the main spring and outside surface of the diaphragm. But "corrosion" there is pretty meaningless verdigris.
On the other hand, there is an easy way for corrosion to get inside your first stage: tank changes.
When you finish boat dive #1, the Divemaster may race along the boat, slipping the gear off one tank and onto the next. The cap NEVER gets placed on the first stage during the change. A little drop of sea water from the wet gear, that falls on the sintered metal filter where the first stage meets the tank, then gets blown inside the mechanism when the rig is pressurized. Do that a few dozen times on a few boat trips, and let your first stage sit in your closet in between trips, and you have "corrosion in your first stage."

Nobody but me changes my tank. I'm polite, and the DM's usually don't get huffy about it. If I'm on a boat where the tanks are refilled from a central large tank during the Surface Interval, I'm religious about removing my first stage, drying the sealing area, and recapping the air opening while it's lying wet on my bcc.

AWESOME explanation. I never knew all of that. Thank you for taking the time to post this. I'm going to get an IP gauge and use it, as well as the check list you linked in to. I will also be paying more attention to my dive gear on the boat. It's funny, you get on the boat as a diver and relish at the thought that you don't have to mess with your gear in between dives; the crew does it for you. I have always figured that the boat crew were careful about gear. Ha! No more of that. Thanks again!