# Quick guidelines for buying co2 regulators off ebay



## neilshieh (Jun 24, 2010)

This thread was written to give people a better understanding on how to search for and determine if a regulator is appropriate for our use. The goal is to score cheap usuable regulators off ebay
1. Entering in "dual stage co2 regulator" will not yield very good results. Most sellers are selling government/lab surplus and don't understand dual stage versus single stage and will not list them as so. Only hobbyists would be more familiar with that term and they'd list their regs for much higher prices.

2. Dual gauge does not equal dual stage. dual gauge, as the name implies, just means the regulator has two gauges. one for reading high pressure (co2 tank pressure) and low pressure (output pressure) For victor regulator VTS means dual stage, SR means single stage. Look at the pictures if the regulator is able to lay flat on the surface it means theres no secondary stage knob and thus it's a single stage. If they took the picture with the regulator sitting up its because there's a secondary stage knob at the back (some sellers might take pictures of it facing up but because of the knob it'll be tilted at an angle)

3. search for [brand] regulator. e.g. victor regulator, matheson regulator, praxair regulator, harris regulator, etc.

4. sort from lowest to highest, and then start going through the auctions/buy it nows.

5. things to look out for: high pressure gauge must read at least 1000 psi (usually co2 tanks have 800 psi), low pressure gauge should read atleast 15-30 psi and maximum of 200 psi. 30 psi gauges usually means the regulator outputs a max of 15 psi. any lower means it outputs <10 psi and is generally not suitable for our hobby. low pressure gauges that read past 200 psi means that adjusting pressure to our usuable range (10-30) psi will be difficult.

6. look at the condition of the regulator. If it looks like it went through hell and back pass on it. If it looks decent, take a leap of faith. generally the nice shiny ones are working but this is not a guarantee. Check to make sure all gauges are pointing at 0 (some gauges may have vacuum pressures, do not worry about these) usually sellers don't know the condition themselves and will refund you if they don't work.

7. ideally a cga 320 inlet would be good but not necessary. most co2 regulators will have the cga number in the serial name something like ***-580-** or **-320-** etc. if you get one without a cga 320 inlet wrenching it off with a pipe wrench or crescent wrench is easy.

8. don't be afraid to message the seller and offer a better price or ask them to ship via usps medium flat rate for 11 dollars. Some of these auctions have been sitting there for a long time, the sellers just want them gone.

9. if it fits the criteria for most of the above, perhaps do some additional research on the model. google the basic series name e.g. victor hpt-500-580-4DK you'd just google victor hpt 500 regulator and you should be able to find technical specs. just check the output psi ranges, input, and connections (you want 1/4 npt connections, vcr fittings are a PITA to convert/find fittings for)

10. snipe the auction or it's a buy it now, buy it. If they allow offers drop the price 10-20 dollars and you have a good chance of the seller accepting.

Hope this helps a few who don't know what to look for.


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## niko (Jan 28, 2004)

And what is a dual stage vs. single stage?


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## BruceF (Aug 5, 2011)

Great info Neil thanks.


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## Tugg (Jul 28, 2013)

niko said:


> And what is a dual stage vs. single stage?


Dual stage regulators are actually two regulators built into one. The first stage knocks the pressure down to a regulated (meaning constant) PSI for the second stage. This helps prevent fluctuations due to changing PSI from the tank due to temp and volume. Two-stages also adds protection from the tank dumping when it gets too low.

A single stage regulator is less expensive, but adds risk and can be more difficult to get a reliably steady output on.


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## neilshieh (Jun 24, 2010)

niko said:


> And what is a dual stage vs. single stage?


To keep it simple, for single stage regulator there's only one stage in the main body to regulate the pressure and for dual stage the gas passes through two stages (second stage is the knob protruding from the back). In terms of performance, *SOME* have experienced end of tank dump with their single stage regulators where when the cylinder is almost out of co2 (pressure is falling below 800 psi) the cylinder will upchuck the rest of its liquid co2 and that sudden rush of co2 into the tank will overgas the tank. I've personally seen a few reports where a user reported experiencing EOTD but I also noticed that they've only experienced it with the aquatek or milwaukee budget regulators. Now I won't go out and say that it's a problem with these cheaper budget regulators but the diaphragms in these budget regulators are smaller and made of neoprene. I can only speculate that since these were specifically made for use in aquariums a few technical shortcomings may be in play. Either way, I personally think single stages are fine for our use and have built a couple as budget regulators for customers. (though the single stage regulators I use are the high end models like the linde cb 200 regulator which have high purity applications and stainless steel diaphragms) Moreover, if you go the single stage route buy an industrial one like the victor SR###.

For dual stage regulators, yes they're more expensive, but the delivery pressure is extremely stable and you can use the co2 from the tank right up to the point where it completely runs out of gas.

For those planning to use the budget regulators, they're usable but I recommend you watch your high pressure gauge. When it starts to drop below the 700-800 psi range its time to get a refill. Take off your regulator, go outside and let the remaining co2 out and get it refilled.

if you want to read more about the difference (http://www.plantedtank.net/forums/showthread.php?t=148509) there should be some threads floating around on APC but they aren't stickied 

@niko btw I wrote a huge reply to your pm the other day but it got deleted somehow and I've yet to write it all up again. Will try to do so soon sorry!


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## niko (Jan 28, 2004)

Hey! Never knew any of that. I guess I've always used single stage regulators. 10-12 of them over the years. Never had a single issue. But this hobby is not, and should be not, about cheap anything. If I ever buy another regulator it will be two stage. Thank you both!


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## christybell22 (Jan 7, 2010)

Is this regulator one I can use?https://m.ebay.com/itm/Praxair-3159...3A7479401115e0aa48e5bb46a5ffe5eab6%7Ciid%3A13

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## hoppycalif (Apr 7, 2005)

That is a specialty regulator with a gauge calibrated to read in liters per minute instead of psi. It most likely has a fixed restrictor in the outlet side, to make it work that way. I wouldn't try it unless I was willing to do some disassembly to remove that restrictor, to replace the outlet gauge with a psi reading gauge, and to add a good needle valve to it. That adds a lot to the cost.


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## Gone missing (Aug 26, 2017)

This might be one of those cases where it depends on how you think. Liters per minute or PSI both just show you what the reg is putting out but in different terms. As long as they are both adjustable, it can then be a matter of how your mind feels about thinking in liters versus
Pounds per square inch? 
On either, it will take a bit of work with the other parts of your system before you find what setting works best for you. And that depends on what is tied on the output side. So on PSI reading gauges, you can get advise to set it at "X" psi While the liter per minutes is likely to take a bit more guessing to start out at some point and see what flow is achieved. Either is likely to then be adjusted to further suit what you see happening on your tank. Want a firm answer as to what PSI to set (even though that is a guess) or do you want to go with experimenting for yourself? Six of one or half dozen of the other according to who you want making that first guess, you or somebody else. 
The whole question of regs is open. I actually prefer to use new regs that have warranties versus the risk of used regs on E-bay. I go down to the local beer supply place and buy new regs for around $50. 
I'm one of the guys who used to work outside with regs and abused the hell out of them, so I don't ever want to buy one of those!!! 
After the hurricanes, there are going to be a bunch of flooded regs that are rebuilt or resold. Not a good time to buy used regs nor used cars for a while without really checking them. Shiny outside but there may be mud in the pistons?


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## asad_200113 (Aug 24, 2017)

This was actually very helpful. Thanks for making this 


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