CO2 guage question

[beerisking]

So I'm just getting into kegging and picked up 2 reconditioned kegs. After I cleaned therm and replaced the seals,I pressure checked them. All seemed to be good and the tanks help pressure for 24 hours. What I noticed was the co2 guage on the tank had dropped about 5 psi over the day. Basically,after I charged the kegs, I disconnected the quick connect and hose from the keg and just left it sitting next to the kegs. The guage was reading the pressure I left the kegs at, but the next day,had dropped some. Is this normal? Is there a leak some where in the regulator as I had the valve shut off at the hose connect? Thanks for the help.

 

[FloppyKnockers]

If you put your tank in the fridge the pressure will show less than what's actually in there (insert science reason here). To find leaks, Spray a star-san mixture on all the fittings and connectors. It'll tell you pretty quick.

 

[day_trippr]

Vapor pressure varies with temperature and percent of fill...

Cheers!

 

[brewprint]

I asked this same question after I threw my tank in the kegerator. It drops when cold. That gauge almost means nothing. It'll stay that way just about till it runs out and just before it does it'll drop way down. Weigh it to find what's really in it.

 

[beerisking]

Thanks everyone. It wasn't the guage for the tank level that changed. It was the guage for the pressure on the line (or tank if it was hooked up). Basically it was set to 25 psi for pressure testing the keg. Once I filled the keg up, I shut the valve coming off the regulator and going to the QD, disconnected from the keg and left it alone. The guage read 25 psi at that moment but was down to 20 psi the next day. I think it does have to do with temperature and pressure change from the tank,but wasn't sure. First time dealing with this.

 

[chickypad]

If you put your tank in the fridge the pressure will show less than what's actually in there (insert science reason here).

No it shows the correct pressure in the tank, which is lower when you put it in the fridge because (as day trippr noted) pressure is a function of temperature. What the gauge doesn't show is the amount of liquid CO2 left in the keg, for that you have to weigh it.

 

[IslandLizard]

Thanks everyone. It wasn't the guage for the tank level that changed. It was the guage for the pressure on the line (or tank if it was hooked up). Basically it was set to 25 psi for pressure testing the keg. Once I filled the keg up, I shut the valve coming off the regulator and going to the QD, disconnected from the keg and left it alone. The guage read 25 psi at that moment but was down to 20 psi the next day. I think it does have to do with temperature and pressure change from the tank,but wasn't sure. First time dealing with this.

Since it was disconnected from the keg, it sounds like your QD/line/valve/regulator leaks a little, not your keg.

 

[brewkinger]

What he said ^

Assuming you have dual gauge regulator.

The gauge that tells you "how much" CO2 you have in your tank... WORTHLESS.
Stamped on the side of your tank somewhere is the weight of the empty tank. Weigh the tank and subtract and you will know how much gas you have.
(Levels of gas will rise after eating beans, broccoli and drinking yeasty homebrews of course )

Like was mentioned, it sounds like you have a leak between the regulator and the QD, which should be easy to isolate. While I agree with the starsan / soapy water option, it does not ALWAYS work well.
I had a leak that I could not find and simply had to start at the regulator and work my way out to the QD. Lucky for me it was the connection between the regulator and the the gas hose.
I discovered that there should be a small tapered nylon washer (that the supply company "forgot" to include with my order and when I asked them for it, they told me that I had to take pictures of the leak and send it to them and then they would send me the 50 cent washer.) When I conctacted another online vendor and asked, they informed me that it WAS necessary and SHOULD have been included. This company sent me 5 of them for FREE.
Needless to say, I have a new keg supply company (RANT OVER)

Inserted washer and problem was solved. I also found that using oetiker clamps at all connections (instead of worm gear hose clamps) was well worth the additional $15 that I spent.

 

[beerisking]

This is what I need to check. The leak is too slow to use star San,so I will start disassembling and see what I find. Thanks everyone.

 

[FloppyKnockers]

If you put your tank in the fridge the pressure will show less than what's actually in there (insert science reason here). To find leaks, Spray a star-san mixture on all the fittings and connectors. It'll tell you pretty quick.

No it shows the correct pressure in the tank, which is lower when you put it in the fridge because (as day trippr noted) pressure is a function of temperature. What the gauge doesn't show is the amount of liquid CO2 left in the keg, for that you have to weigh it.

Like I said....Science.

 

[IslandLizard]

A slight pressure loss over 24 hours, when disconnected from the keg, is almost inevitable and not the end of the world. The volume lost from that maybe totally negligible, even over a year. Those very small leaks are very hard to trace, they are too slow to bubble a soap solution. Check your clamps, all joints for adequate teflon tape, and washers where needed. From the factory, you may not even get 2 full turns of teflon tape. 3-5 are usually needed on Chinese import fittings.

If you have a bleeding/over-pressure valve on your regulator, they are notorious for getting stuck a bit open. Got to trigger/pull them a few times to get them seated right. Some can be a bit too touchy too (weak spring).

 

[cyberbrew]

(insert science reason here).

PV=nRT