User changeable o-rings

[buddhasummer]

You need these, you'll not get all O rings off with just your fingers:

Three Piece Brass O-Ring Pick Set | Dive Gear Express®

I use this grease:

Tribolube 71 O2 Compatible Lubricant | Dive Gear Express®

 

[buddhasummer]

Check out this video:

 

[Angelo Farina]

As you see from this nice video, changing the O-ring on the male threaded end of the hose (first stage) is very easy.
But, as said, this is static and usually has never problems...
Instead changing the O-ring at the second-stage end of the hose is much more tricky, and requires to have proper tools.
But this is a dynamic O-ring, so it must be mounted perfectly clean and properly lubricated. And, being dynamic, it is much more prone to failure than the first one.
In conclusion, in my "save a dive" bag I carry a spare hose, not the O-rings. If the O-ring at the second stage side of an hose fails, on the boat I simply change the hose, and I will take care of replacing the O-ring where back on the ground.
Fiddling with that tricky O-ring replacement on a boat rolling on rough sea can be really nauseating, and the risk to loose your tiny O-ring is large.
Finally, I had more often a hose failure (due to mishandling of the tank with the reg mounted) than an O-ring failure.

 

[Lorenzoid]

So none of the o-rings is user replaceable without training? If I have a leak in the valve, it is not possible to know that the appropriate o-ring is X, buy it and replace it?
. . .

Yes, so long as you are sure you know which is X. And you might need to keep a supply of not only X but also Y and maybe Z, too. X, Y and Z each may be characterized by a unique combination of: size (there may be two or three different sizes among those you want to replace), hardness (you might need to keep some o-rings that are the same size but of two different hardnesses, so you need to avoid mixing them up), and material (e.g., Viton). What you want to do is easy, so long as you acquire the right set of o-rings and make sure you know which goes where in your reg set.

 

[David Novo]

As you see from this nice video, changing the O-ring on the male threaded end of the hose (first stage) is very easy.
But, as said, this is static and usually has never problems...
Instead changing the O-ring at the second-stage end of the hose is much more tricky, and requires to have proper tools.
But this is a dynamic O-ring, so it must be mounted perfectly clean and properly lubricated. And, being dynamic, it is much more prone to failure than the first one.
In conclusion, in my "save a dive" bag I carry a spare hose, not the O-rings. If the O-ring at the second stage side of an hose fails, on the boat I simply change the hose, and I will take care of replacing the O-ring where back on the ground.
Fiddling with that tricky O-ring replacement on a boat rolling on rough sea can be really nauseating, and the risk to loose your tiny O-ring is large.
Finally, I had more often a hose failure (due to mishandling of the tank with the reg mounted) than an O-ring failure.

My point was on the male end (hose to tank) as the other seemed trickier (which was confirmed in this thread).

Yes, so long as you are sure you know which is X. And you might need to keep a supply of not only X but also Y and maybe Z, too. X, Y and Z each may be characterized by a unique combination of: size (there may be two or three different sizes among those you want to replace), hardness (you might need to keep some o-rings that are the same size but of two different hardnesses, so you need to avoid mixing them up), and material (e.g., Viton). What you want to do is easy, so long as you acquire the right set of o-rings and make sure you know which goes where in your reg set.

Hence my question on which I needed for each application. I may be wrong but it seems that for a specific end of a specific hose, it is always the same.

 

[Angelo Farina]

My point was on the male end (hose to tank) as the other seemed trickier (which was confirmed in this thread).

True, but I did never see that O-ring failing on a properly assembled reg. I had never any need to change these O-rings. Usually the hose becomes old or damaged, and needs to be replaced before this static O-ring has any problem.
Instead at the other end the dynamic O-ring must be replaced at each service, which means every year or perhaps every two years maximum.

Hence my question on which I needed for each application. I may be wrong but it seems that for a specific end of a specific hose, it is always the same.

Not sure they are always exactly the same. Different hose makers could use different O-rings. The external diameter must match the reg, which is standardised, but the inner diameter must match the groove behind the threaded end of the pipe, and here you can get differences...

 

[tursiops]

Not sure they are always exactly the same. Different hose makers could use different O-rings. The external diameter must match the reg, which is standardised, but the inner diameter must match the groove behind the threaded end of the pipe, and here you can get differences...

I would not worry about this unless your reg is very very old or very very unusual, thus possibly requiring an odd-ball hose. Today's regs -- with a few exceptions like Poseidon -- are standarized on their HP and LP ports as are the hoses that fit them.

OP, what is your reg that you are getting spare o-rings for?

 

[David Novo]

I would not worry about this unless your reg is very very old or very very unusual, thus possibly requiring an odd-ball hose. Today's regs -- with a few exceptions like Poseidon -- are standarized on their HP and LP ports as are the hoses that fit them.

OP, what is your reg that you are getting spare o-rings for?

Apeks FSR / XTX

And I meant for a given model, meaning I know all the variables beforehand that I expect to define the O-Ring I need. I needed someone to tell me which is the latter

Anyway got the message. Do not touch the o-rings without further training.

 

[tursiops]

Fair enough. Which reading do you recommend?

The gold standards are:
SCUBA REGULATOR MAINTENANCE AND REPAIR by Vance Harlow
Regulator Savvy (Spiral Bound)
Another useful source of info is:
https://www.scubaboard.com/community/threads/regulator-inspection-and-checklist-rev-8.346813
If you only read one thing, read this:
https://www.scubaboard.com/community/threads/o-rings-for-divers.553724

For the male ends of the hoses, where they go into your first stage, there are just two sizes; the o-rings are A011 (LP port, 3/8 UNF threads) and A012 (HP port, 5/16 UNF threads). The former should be N70 durometer, the latter N90. The very smallest amount of lube on them (silicone OK for air use, Christolube or Tribolube for Nitrox), just enough to make them shiny (slippery). They are static seals, not sliding seals, but you want them to not get torn up from sticking when you tighten the port plug or the hose. Don't under-tighten or over-tighten; 30-35 inch-pounds or 3.4-4.0 N-m is about right. Too much and the o-rings tear/break/crush, and you've got a leak.
NOTE: some regs have a 1/2 UNF LP thread; this takes a A013 o-ring.

The female ends of the hoses are a different matter:

1. the hose-2nd stage connector is tough to replace (A010 N70 o-ring), but can be done with care. Just carry a spare hose.
2. the hose-LPI QD connector is REALLY tough to replace (also A010). Just carry a spare hose.
3. the hose-SPG connector has a small "spool" or "stem" in it with two small A003 o-rings on it. Just carry a spare spool, or better, a spare hose. This, by the way, is the first-most common o-ring (one or the other or both) to fail and release bubbles, in my experience. the second-most common failure is item #2 above.

Use brass or plastic o-ring picks, not steel; don't scratch the o-ring groove!

 

[herman]

Some grease will not hurt. But these are STATIC O-rings, once they seat under pressure, they will stay there for many years without problems.
What can happen, if they are not lubricated, is that the rubber will stitch to the metal so much that, when the hose is unscrewed, some rubber will remain attached to the metal, with two bad consequences:
1) The O-ring will be damaged, hence it will not seal well anymore
2) The conical surface in the reg will be "dirty" of rubber particles, hence it will need to be cleaned/polished before installing a new hose (or plug)

It's been a while since I kicked this topic so I will do it again, it's s little understood subject,
Most orings used in scuba are, contrary to common understanding, dynamic, very few are static. The most common static ones are the yoke and DIN to tank oring. Contrary to popular belief, hose orings are not static but are in fact dynamic. While in service they are static, however, to be truely static, an oring can never,....the key word here is never.... move past their mating surface and that is the rub. While being installed, the hose oring does in fact move past its mating surface which makes it dynamic at that point and it needs to be lubed. Many get away with no lubing hose orings, mainly due to residual lube remaining in the port but to do it correctly, the oring needs to be lightly lubed.