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How many PSI should a full 5# CO2 bottle read?

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Not sure what's up...I have a loaner 5# CO2 bottle and I just had it filled a couple weeks ago. When I attach the reg. it shows around 1000psi. The tank lasts less then a month. I checked for leaking but didn't see anything.
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Plant Clown
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Or the gauge is off. I've had regulators read between 700psi and close to 1000psi. Next time you refill, see if it reads the same. If so, it's a little off. Which is fine, because all you need to know is if the pressure starts dropping, which will happen when it's almost empty. With that in mind, the gauge could be completely blank as long as the little dial functioned.
 

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A 5 lb tank will register the same on the gauges whether or not there is 5lbs or 1lb. The pressure doesn't start dropping until the last of the liquid evaporates, and there is only gas in the tank. If your tank is not getting filled all the way, it could only last a couple of weeks, but still read 800-1000 psi when you bring it home from refill. I have had that happen before. Weighing it before and after is the only way to be sure you are getting it filled. It also depends on the ambient temperature. Higher temperature, higher pressure.
 

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Plant Clown
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You have a leak. A big one. spray every single connection with soapy water. Since you said you've checked for leaks before, you must have missed checking a connection.

If there are any animals living in the tank (anything at all including snails) you didn't have the CO2 turned up a tiny fraction of the way it would take to gas out your cylinder that fast, so that's not an issue.

It's possible the refill place severely shorted you on CO2. Far more likely, though is a huge leak. In fact, something as big as it would take should be audible. Get on the floor and listen very closely to every part of the rig and line, starting with the connection from the cylinder to regulator. And then soap test.
 

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How did you check it for leaking? How much does it weight? It should be stamped somewhere on there saying the "tare" weight which is the cylinder, then add 5# and that is your full weight. Should weight roughly 12lbs *full* if it is an aluminum but all tanks are different some weight 12lbs empty.
 

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Discussion Starter · #10 ·
I'll check again. I'll check everything from the tank to the reg. to the line to the reactor. The tank is steel...I'll weight it next time before taking it to the shop for a re-fill and again when I get home. I don't think I am being shorted...the place I go to is a very reputable welding shop...but then again, you never know.
 

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It may have been closer to 800...I just know it was close to 1000. It's at 400 now and it's only been a couple weeks. I need to get a bubble counter maybe to make sure I don't have the CO2 turned up too much even though the fish seem fine. I thought that a 5# tank should last several months...not weeks.

Yeah, you have a leak. Check the joints between your soleniod and bubble counter, if you have them. Maybe even the joints between the regulator to the tank.

To check for leaks between the regulator to the tank, turn off the tank valve. Then, turn off the working pressure on the regulator. Let it sit overnight, 12 hours+. Now, the tank pressure on the gauge should remain the same after 12 hours+. If not, you have a leak between the regulator to the tank. Maybe you didn't change your CO2 tank washer after the refill.

To check for leaks between the regulator to the needle valve, turn off the tank valve. Increase your working pressure to a higher pressure, 30 psi to 40 psi. Makes sure your soleniod is closed. Let it sit overnight for 12 hours+. In the morning, the working pressure gauge should be reading the same pressure as of last night. If not, you have a leak somewhere between the soleniod and the regulator. Do the same procedure for the needle valve (needle valve close while the soleniod is open). The working pressure should remain the same.
 

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Discussion Starter · #12 ·
Well...I guess I'm a dumbass...it was leaking at the connection between the tank and the reg. Some teflon tape took care of it. I checked it there last time when I first got the tank...maybe I had it threaded just tight enough then that it didn't leak right away though the CO2 only lasted a few weeks like this time. Guess a lesson learned. I still wanted to find out what the pressure was supposed to be on a full tank...for some reason I thought it would be higher. Guess I am just use to SCUBA and SCBA tank that have pressures of 3000 and 4500psi.
 

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Plant Clown
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Teflon tape won't cut it. All you need is a nylon washer.

The reason teflon won't cut it is that the CGA320 connections are parallel threads, instead of tapered threads like NPT connections. They need some sort of malleable material between whatever they're pulling together in order to create a seal.

If you have a nylon or paper "crush" washer (or a permaseal) between the regulator and cylinder, all you need to do is torque the heck out of it with a large wrench. If you don't have one, you need to go get one. Wherever you fill up or swap your tank has them, so just ask for a couple. You should put in a new washer every time you fill your cylinder.
 

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Discussion Starter · #15 ·
It has a nylon washer and it's torqued enough that the washer is imprinted from the reg. I don't know. The leaked did stop though. I really cranked down this time too so maybe it's just from being tighter, maybe from the tape, maybe from both...I don't know...it's not leaking now so that's good enough for me. I'll definitely get more new washers next refill...this one is reused from last time. This tank can't use a permaseal, I'm hoping my 10# tank can...I never looked. I am waiting for them to hydrotest it. Should be done soon I hope. There was like a 4 week back log on testing. That's why I have the 5# loaner.
 

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Plant Clown
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I actually don't like permaseals, as the only one I've ever used broke. Nylon washers, however, have never let me down.

Just take the tape off the threads of the 5# before you return it to them. They might be really annoyed at you.

I've never had a leak at the CGA connection, by the way. I just torque the heck out of the nut and walk and turn on the cylinder.
 

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I use the paper washer that comes on a tank refill but you need 2 wrenches and you have to really crank on it and you'll be fine but if you use a single wrench you are likely to get a leak after a week or so and if it goes unnoticed the tank will be empty in couple of days.
 

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Plant Clown
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Can you explain how you'd use two wrenches? I just crank down on the CGA nut and the cylinder is heavy enough that it won't spin if I'm pushing downward.

As for nylon washers, item # 360386799207 on Evilbay is 10 washers shipped for $4. Or do a search for nylon washer CO2. They come in that normal yellowish color, btw, not the red that you see in the pic.

If you mess with your reg a lot (like me), you may want to switch to a new washer before it's time to refill the tank. So even if you get one free with every refill, it's good to have extras.
 

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Can you explain how you'd use two wrenches? I just crank down on the CGA nut and the cylinder is heavy enough that it won't spin if I'm pushing downward.

As for nylon washers, item # 360386799207 on Evilbay is 10 washers shipped for $4. Or do a search for nylon washer CO2. They come in that normal yellowish color, btw, not the red that you see in the pic.

If you mess with your reg a lot (like me), you may want to switch to a new washer before it's time to refill the tank. So even if you get one free with every refill, it's good to have extras.
I use size 9 o rings from lowes 2.50 for 10, no leaks in 8 months.
 

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Am I just lucky that I live in areas where Airgas and Haun have outlets? I've welded for 30+ years and bought probably 1000 lbs of CO2 in my life, in both Charlotte NC and here in Syracuse, and never had an issue. They take used 10 lb bottles and just swap them out for new ones for $18. They sell washers for pennies. I would never go to the trouble of buying an aluminum bottle because I wouldn't trust the local homebrew store to do me right. And I don't think Airgas or Haun will touch them. This is a curiosity to me.
 
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