cdharris
Diver
Posts: 17
Joined: Sun Jan 03, 2010 3:48 am
First Name: Clay

USD Aquarius problem

Tue Jul 23, 2013 7:54 pm

I own an (externally) almost-like-new 1977 USD Aquarius that has a slow leak from the 1st stage drain ports. I have overhauled the reg replacing all o-rings with 70 durometer in-spec parts. Currently, at 1500 psi (according to my trusty SeaVue gauge), I have the IP set at around 130. Still leaking.

The regulator came to me from someone who used it on an argon bottle. It had a moderate amount of verdigris on the interior (nothing on the exterior) that I initially blamed for the slow leak. This corrosion mostly came off pretty easily with a vinegar bath and ultrasonic cleaning. Ironically, the leak was slower BEFORE the cleaning and overhaul.

However, I did have to use a plastic toothbrush to really get the crusties out of the piston chamber. Even before cleaning, the chamber showed signs of both circumferential and longitudinal scratches -- although all rather light. In fact, there is only one longitudinal scratch and it is fairly close to the end cap. The chamber otherwise looks and feels completely smooth. Is it likely that these scratches are to blame, or more likely that either the piston or piston chamber is out of spec?

That's about all I know. Can anyone make suggestions as to what I might do to solve this problem? Polish chamber? Use 90 durometer o-rings? Goop up the chamber with so much silicone you could drown in it? Drive a bulldozer over it and buy an Atomic T3 Titanium Regulator?

I love this little reg, and want to use it on my pony bottle when I'm diving vintage. I suppose if it just leaks this much and no more for an hour long dive, I can cope. I'm guessing it would amount to a few full breaths of lost gas. The original piston o-ring showed no obvious signs of wear, so I'm not really concerned about the faint scratches causing a catastrophic o-ring failure.

But it is really tough on my OCD self to look down and see that constant stream of bubbles when the reg on my back is 20 years older and still leak free.

I also own a younger Aquarius (three LP ports rather than two) that I could use to troubleshoot this one, but that seems like a lot of trouble and might not tell me -- in my ignorance -- a cotton-pickin' thing.

Any takers?

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antique diver
Master Diver
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Re: USD Aquarius problem

Tue Jul 23, 2013 11:21 pm

I would start with replacing the two orings on the piston again, using a little more silicone grease for lube, not a spray. There could be a blemish on one of the new O-rings that you originally used. Also look closely for corrosion or scratches in the small bore where the piston stem rides in the body.

I am pretty sure that the softer 70 durometer orings will make a better seal than 90's.

What did you originally use for the lubricant?

There are varying viscosities of grease, and while I prefer a light grease for piston lubes (so as not to impede the movement of parts) the heavier/thicker DOW-111 could possibly be more effective at sealing up minor scratches in the metal bores. Also look for tool marks on the piston where someone may have scratched the surface taking off orings. Piston would be easier to find than a good body. I think I have one.

Good luck!
The older I get the better I was.

cdharris
Diver
Posts: 17
Joined: Sun Jan 03, 2010 3:48 am
First Name: Clay

Re: USD Aquarius problem

Wed Jul 24, 2013 1:14 am

Much obliged. In my haste, I did not really give "the small bore" close scrutiny. That seems like a good suspect. On the other hand, I have seen no scratches or irregularities on any moving parts, or o-rings. However, I will give the small bore a good cleaning and inspection, followed by new o-rings and a tad more silicone. I had already moved up in viscosity to Dow-111 (equivalent), so that isn't likely to help, but is still good advice. I was a little sparing with the goop though, owing to Harlow's and Wolfinger's admonitions.

Hopefully, I'll have time to tackle this tomorrow. Thanks.
antique diver wrote:I would start with replacing the two orings on the piston again, using a little more silicone grease for lube, not a spray. There could be a blemish on one of the new O-rings that you originally used. Also look closely for corrosion or scratches in the small bore where the piston stem rides in the body.

I am pretty sure that the softer 70 durometer orings will make a better seal than 90's.

What did you originally use for the lubricant?

There are varying viscosities of grease, and while I prefer a light grease for piston lubes (so as not to impede the movement of parts) the heavier/thicker DOW-111 could possibly be more effective at sealing up minor scratches in the metal bores. Also look for tool marks on the piston where someone may have scratched the surface taking off orings. Piston would be easier to find than a good body. I think I have one.

Good luck!

cdharris
Diver
Posts: 17
Joined: Sun Jan 03, 2010 3:48 am
First Name: Clay

Re: USD Aquarius problem

Wed Jul 24, 2013 7:24 pm

I have now put in several more hours on this Aquarius. I have replaced the o-rings three times. Gave it two more thorough ultrasonic vinegar treatments (which it did need). I even replaced the piston seat just for the heck of it. It still leaks. A little less than before, but still leaking.

I can see that in the smaller throat of the piston bore there is a slight scratch, but other than that it is now smooth. Using a pen light at a high oblique angle really highlights the flaws, but there just isn't much to see thanks to the cleanings.

Before, it did have a bit of additional corrosion in the bore that I had missed, but like I say, removing it has done little or nothing for my leak. I have examined all sealing surfaces very closely with no hint of a problem. I looked in Harlow again, and according to p. 163, it is probably the smaller piston o-ring (-007), based on a stable IP.

At this point, I guess I am resigned to swapping parts around between regs and seeing what happens. I wouldn't mind so much if it were something that I really cherished. At this point though, it is a mystery that I want to solve.

I do have one additional question if anyone is game. I don't seem to be able to get the small o-ring on w/o putting the o-ring interior at risk of marring by the piston's hard seat. I've looked (with 10X and 35X mag.) at all three "used" -007 o-rings and none were marred during installation. Still, I'm curious if anyone has a good method for this particular piston.

Likewise I'm open to any additonal help on what the problem might be with this reg. Thanks.

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Ron
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Re: USD Aquarius problem

Wed Aug 14, 2013 8:33 pm

Hey CH! Let us know how you fare with troubleshooting. I had an aquarius do this to me, and my problem ended up being a little flaw in the volcano orifice. I used a dowel with a bit of 2,000 grit sandpaper glued to it, and that resolved the issue. If you can, try to get a good look in there with a rifle bore inspection light, or something improvised, and see if that orifice looks nicked.
The impossible missions are the only ones which succeed. -JYC

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