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-   -   Do I have a CO2 Leak? (http://www.homebrewtalk.com/f35/do-i-have-co2-leak-382050/)

NLBrewer 01-16-2013 10:02 PM

Do I have a CO2 Leak?
 
I just started kegging and am concerned that I may have a co2 leak. 2 weeks ago I put my first keg into my kegerator and the regulator was reading just over/at the 600 psi line, or above the red. I keep my regular/co2 tank inside my kegerator. Pressure remained constant for the first keg. I added a second keg to the system 5 days ago and for the first couple of days it appearted the pressure was also pretty much constant. I checked it yesterday and it had dropped below the red line and I checked again today and it's after dropping a little more, now at about 425. My fridge temperature is at 41 degrees.

To carb my kegs I put them at 30 psi for 24 hours and then back to serving at around 10-11psi. I would guestimate I have gone through about 1/3 to 1/2 of the first keg and about 6 glasses out of the second. The only other co2 I used would have been to seal and purge the kegs after I sealed them.

Here's a picture where my regulator pressure is now. Should I be worried?

[IMG="http://www.flickr.com/photos/92283963@N03/8387153433/"]

Reno_eNVy 01-16-2013 10:12 PM

You most certainly shouldn't be concerned. PV=nRT... on other words, as temperature (T) goes down, so does pressure (P) and volume (V). I had the same worry when I started kegging since I used to keep my CO2 tank inside the fridge.

But just to be sure take a spray bottle with some sanitizer solution in it and spray areas where CO2 could possibly leak: gas quick connect, keg lid, any point that gas line connects to something else. It will help you see if anything is leaking as it will produce a bunch of bubbles in the liquid. But I think it's just because you're keeping the CO2 tank in your fridge.

Hope that helps :mug:

NLBrewer 01-16-2013 10:23 PM

Thanks for the reassuring response :) I guess I'll leave it for another few days and see how it goes. When I put the second keg in I put soapy water on the keg lid/posts and line and didn't not have any leaks but I did not check the lines back to the manifold and regulator as I figured they were good as they came pre-assembled.

I don't plan on any more beers tonight - could change though ;), should I expect any drop in pressure by tomorrow or should it remain fairly constant at that pressure?

I've read other threads where people are getting 5-8 kegs out of a 5lb tank, I hope to get at least 5 as co2 isn't cheap for me - was $41 to fill the tank last time!

Yooper 01-16-2013 10:26 PM

I've often said (only half jokingly) that the best way to deal with the high pressure gauge is to cover it with duct tape.

The reason is that it's totally pressure/temperature dependent. Right now, my completely full 5 pound tank reads 750 psi. If it put it in the fridge, it'll go lower. And it will stay where it is until it's almost empty, and then go to 0 in an hour!

The reason is that co2 is a liquid, but dispensed as a gas. The high pressure gauge is useless, unless you want confirmation that the tank is empty. When you fill the tank, it's given to you by weight. So, a 5# tank should hold 5#s of gas. If you weigh your tank, without the regulator, and subtract the tare weight stamped on the side, then you'll know how much gas you have. The high pressure gauge isn't useful at all for that.

MNRon 01-17-2013 02:56 AM

$41 to fill a 5lb tank sounds kind of high, I just filled my new one for $11. You might want to check around.

NLBrewer 01-17-2013 11:28 AM

I checked my gauge again this morning before leaving for work and it doesn't appear to have moved overnight - what you've guys said appears true. I'll just relax and have a beer.

Hockey is back on Saturday night, habs vs leafs, I'd say I'll be having more than one :)

zachattack 01-17-2013 12:55 PM

1 Attachment(s)
Quote:

Originally Posted by Reno_eNVy (Post 4793072)
You most certainly shouldn't be concerned. PV=nRT... on other words, as temperature (T) goes down, so does pressure (P) and volume (V).

Not to nitpick, but: since this is a gas/liquid system, the ideal gas law is irrelevant when looking at the total mixture. If you had a cylinder with pure gas in it (once you run out of liquid CO2), the pressure will fluctuate linearly with temperature as you described.

When there's liquid present, the fluctuations are due to changes in the vapor pressure of liquid CO2 (vapor/liquid equilibrium) with temperature, not the gas expanding/contracting.

http://en.wikipedia.org/wiki/Carbon_dioxide_data#Liquid.2Fvapor_equilibrium_the rmodynamic_data

Attached is a quick plot I put together using the data from Wikipedia. As you can see, it's not linear.

NLBrewer 01-17-2013 10:14 PM

I checked it again this evening and it has dropped further and sits at the 400psi mark. The fridge is no colder so I'm not really sure what would explain this. Back to thinking there is a leak. I'm gonna dry some soap water this evening to see if I find anything.

Shooter 01-17-2013 10:23 PM

Check it with some soapy water or spritzing with StarSan can work. The pressure should drop when placed in the fridge, but should stablilize. If it keeps going down over several days, there is something else going on. From your original post it sounds like it has been at cold temp for two weeks, it should have evened out after a day or so. I would begin by checking the lines and the connections at the newly added keg, since your problems seemed to start after the addition of that keg. If that doesn't reveal the problem, start checking the other areas.

Reno_eNVy 01-17-2013 10:40 PM

Quote:

Originally Posted by zachattack (Post 4794858)
Not to nitpick, but: since this is a gas/liquid system, the ideal gas law is irrelevant when looking at the total mixture.

Ah yup... yup, ya got me :mug:


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