Question Used SPG?

[aangaroo]

Hi,

I found a pretty good deal locally for a used Highland SPG for $30. From the picture, it looks pretty scratched up. Is there any problem with buying a used SPG? The owner says the last time it was used was about a year ago.

 

[Brett Hatch]

There's nothing inherently wrong with a used SPG. If I was gonna buy one that banged up, I would bring along another one to compare it against, and only go through with the purchase if they read close to the same pressure on a tank. Say, within 100 psi or so.

If you do buy it, take this opportunity to replace the spool. They cost like $2, and sometimes local dive shops will have a box full of them and just give you one if you ask. No special tools needed, just a pair of wrenches.

By the way, DGX sells good-quality new SPGs for around $60. So that might be another good option for you.

 

[happy-diver]

When the build up of hardened grease rubber and other detritus prevents sealing
I leave a cotton bud soaked in phosphoric in there for a while until it sparklearkles

even if it does seal or vinegar preventative

 

[halocline]

You might be able to use micro mesh to get some of those scratches out. You can also sort-of check the accuracy if you have another SPG and a 1st stage with 2 HP ports. Put both SPGs on the 1st stage, attach it to a full tank, pen the valve, let it pressurize, then close it. (If the pressure starts going down you have a leak) Compare the readings on the two SPGs, then tap the purge on one f the 2nd stages so the pressure drops a few hundred PSI, compare again, repeat until zero. If they read the same at all pressures, they’re probably good. (How’s that for a highly scientific process, lol) If they disagree, fins yet another SPG, maybe a newer one, and check again. Eventually you get a good sense of which one is out. I have 5 or 6 SPGs and I go through this with them from time to time. Usually, my experience with older ones is that they tend to read high at higher pressures, are about even in the middle, and low on the low end. That’s useable IMO, but I’ve also had some that read high all the way down, and those I toss.

 

[Still Kicking]

Headlight polishing kit with rubbing compound or white toothpaste will help with the plastic scratches.

 

[Allen-1]

There's nothing inherently wrong with a used SPG. If I was gonna buy one that banged up, I would bring along another one to compare it against, and only go through with the purchase if they read close to the same pressure on a tank. Say, within 100 psi or so.

If you do buy it, take this opportunity to replace the spool. They cost like $2, and sometimes local dive shops will have a box full of them and just give you one if you ask. No special tools needed, just a pair of wrenches.

By the way, DGX sells good-quality new SPGs for around $60. So that might be another good option for you.

I don’t understand “spool” in this context. Could you explain please?

 

[Still Kicking]

I don’t understand “spool” in this context. Could you explain please?

 

[Wants2divemore]

Here's a video from Dive Rite about changing the air spool

 

[tmassey]

I don’t understand “spool” in this context. Could you explain please?

To expand on @Still Kicking ’s photo: the spool goes between the SPG and the end of the HP hose. It allows the SPG to rotate on the end of the HP hose. It is a required part for it to seal. There are a few different styles, and not all work for each combination of hose and SPG. Replacing the o-rings on spools is theoretically possible, but 90-duro rings tend to break first in my experience, and 70 duro wear out quickly, giving you the common champagne bubbles from that spot.

That’s a plastic SPG. DGX has those for $50. Unless you’re *really* hurting for money, I’d buy that new: $20 off for a device in that condition isn’t worth it — to me, anyway. Personally, I’d spend the extra $10 and get the brass and glass one. *So* much more durable. The only advantage of the plastic ones are that they are thinner, but that’s never something that actually provides a value to me. So I stick to the brass and glass. YMMV, of course.

ETA: oh, and the DGX gauges include a brand new spool…. For that price, just get the new one…….

Plastic:

DGX Thin SPG, Naked

The compact thin submersible pressure gauge has a 2-inch diameter and 1.75-inch face with a polycarbonate plastic face cover and nickel-plated brass housing. Available in PSI or Bar with choice of white or black face.

www.divegearexpress.com

Glass

DGX Black Face Premium SPG, Naked

The naked Black Face SPG is now available from Dive Gear Express in two sizes and your choice of PSI or BAR.

www.divegearexpress.com

 

[mr_v]

You can restore the SPG just like you'd restore headlights or anything with plastic, acrylic. Do this at your risk - typically, my restored SPGs are on the test bench, as I usually dive "brass-and-glass." The picture below reflects the following grit sequence:

- 400
- 800
- 1000
- 2000
- 3000
- 5000
- 7000

The photos don't do the result justice - it comes out nice and clear, as if it were brand new.

When you restore, you remove a thin material layer which may weaken the lens. While it is not a problem on car headlights or watches, I am not sure how it affects SPGs.

I do not know what your setup is like, but you can find SPGs for under $50 so buy new ones if you can. I also buy button SPGs for my stage bottles or as x-mas presents for save-a-dive kits. The restoration shown above is more about having free time than anything else ;-)