I'm pondering the best way to go with CO2 gas equipment. I've narrowed down to a couple of choices and would love some opinions.

Option 1. Tunze regulator, incl needle guage: http://www.tunze.com/149.html?&L=1&C...-infoxunter031 (the regulator not the gas bottle); OR

Option 2. Harris 601 regulator http://www.harriscal.it/RE%20%20cili...lator%20EN.htm; with the Swagelok needle valve.

(Looking at second hand regulators as well, but both above options are new and a decent price and I think I'd prefer new.)

Option 2 would cost a bit more, but not much more than option 1.

I'm aiming for a fire extinguisher 3.5 or 5 kg (second hand) as new or hired CO2 cylinders cost a lot here. There's a local chap who'll test and refill it for me and I'll hopefully be able to cajole him into checking the regulator connections are in place.

What do you think - go for option 1 or option 2 (want it to last forever).

Don't have any experience with those regulators for use with an aquarium. I use a Milwalkee regulator for mine.

I have calibrated some Harris regulator flow meter/regulator combos at work. The only issues we've had with the Harris units at work is that whoever assembled the seperate components used some sort of sealing glue instead of teflon tape on the threaded connections which makes it difficult but not impossible to change something like the needle valve without damaging anything. The other issue is that they publish an accuracy of ±10% on the flow meter, and one would think that 95% of them would meet that tolerance, but in my experience I have found that the spec would have to be increased to about ±14% inorder for 95% of them to meet the tolerance. Neither of these should present a problem for use on the home aquarium.

As for the swagelok type connections, I recommend the more expensive steel over brass only if you plan on disconnecting and reconnecting the swagelok connections frequently. The theads on soft brass wear much faster than the threads on steel. Swagelok connections are my prefered type of connection because they are very quick and easy and seal well even under very high pressure.

Thanks for the info. BTW, I thought that Teflon tape was a no-no for gas as tiny bits of tape could get caught in the gas line, especially risk of clogging the needle valve. (Teflon being designed for water plumbing.) But I'm not even a user (yet) let alone an expert

Some have said this, I've never seen it and never had an issue and I've been at it a long time and had done many CO2 tank set ups.
Keep it on the threads , I think you'll have little issue.

Regards,
Tom Barr

Teflon tape should always be used with any tapered pipe thread connections, of which the most common are: 1/8 NPT, 1/4 NPT, 1/2 NPT (NPT=National Pipe Thread). NPT connections are tapered at 1/16" per inch, meaning that the diameter at the one end is slightly smaller than the other end. Tapered pipe threads use the threads themselves to make the seal and do not bottom out. Failure to use teflon on NPT threads will almost always result in leaks.

In general teflon tape should not be used with any other type of straight threaded connectors. (It will usually cause leaks). There are many hundreds of non-NPT connectors such as: Swagelok, BSPT (Brittish Straight Pipe Thread), Prestolok, or anything that uses a rubber o-ring or gasket to make a seal. Non Tapered pipe threads do not use the threads to make the seal, instead they use the threads only to apply a force to squeeze two surfaces together and the surfaces make the seal. Teflon tape usually prevents this seal.

So if it's not a NPT thread do not use teflon tape unless directed to by the MFR.

Most regulators have NPT connections for the pressure gauges and for the output line, but usually have a different type where they connect to the bottle.

When using teflon tape, completly clean the threads you are going to apply it to. Do not just add a layer on top of an old layer of teflon or it will leak. When applying the teflon to clean threads wrap it flat and evenly around the thread streatching it slightly to get a nice smooth even coat of the tape around the thread two to three layers thick. If you do it like this and tighten the connector good and snug, you will get a leak free connection the first try every time.

If you reuse old teflon tape, fail to clean the threads (both male & female), wrap the tape past first thread at the end of the pipe connector, or just plain use way too much thinking the "bigger the blob the better the job" you will get little bits of teflon that are cut off by the threads while making the connection. These bits if loose can blow down stream and can but usually don't get caught on a restriction (depends on what the flow restriction is) in the line and can cause a clog. I would think if this worst case were to happen it would be immediately obvious by the lack of gas flow. Bits caught in your needle valve can prevent it from sealing properly when you use the needle valve to shut off the gas.

So yes most definately be careful to keep the line free of debris that may cause you problems.

I was working for NASA years ago when teflon tape first began to be available. The mechanics there informed me that the tape did not act as a seal, but as a lubricant, allowing you to to tighten the fitting more. Before the tape was available we used various other "pipe dopes" to also act both as a lubricant and as a sealant. And, later, when "Loctite" became available and was formulated for a variety of uses, a Loctite made just for pipe fittings came into wide use. So, today there are several good options for sealing pipe threads. I think if you keep the teflon tape limited just to the male threaded fitting threads, with no overlap over the end of the threads, it isn't possible for a pressurized connection to allow bits of tape to get into the gas path. A vacuum connection would be more likely to allow bits to be sucked into the gas.

You are exactly correct as to why the teflon helps the seal. That is why it is also referred to as anti-seizing tape. (hopefully I spelled that right). It allows the tapered threads to screw in further without the threads locking into place, which improves the seal.

But as I was saying this only works with tapered pipe threads. I have seen many people apply teflon tape to non-NPT threads and have nothing but leaks as pressure is increased. This is because the teflon gets in between and causes a tiny gap between the sufaces that are supposed to be in direct contact with each other to seal.

So......tape is good.
Also, make sure to add that plastic seal in between the tank and the reg.


Regards,
Tom Barr

Sorry if I went beyond what is needed with my explaination.

I am an expert in precision pressure measurments with a great deal of experience in precision thread standard measurements.

Excellent stuff. I've been a bit nervous about setting up CO2, but am getting a lot more confident now. Thanks very much everyone for the terrific advice.