# Filling CO2, weights, tare, etc... sure I got it right but want to verify

### Help Support Homebrew Talk:

#### TomSD

##### Da Geek
OK I've taken my 10# bottle to two places so far to get it filled and both of them messed it up.

First one seemed to know what he was doing but the tank was low so I only got a partial fill. He actually weighed before and after and only charged me partial.

The keg place I went to today just totally amazed me though. Long story short I went three freaking times and I only have about 2# - 2.5# over tare.

Now the part I want to clarify that I'm sure I already know. I've been wrong before though so might as well make sure...

CO2 is measured in weight... not PSI, not some other funky unit. Simple weight. The bottle is at its tare weight (stamped on the bottle as TW) when it is empty and at tare weight plus bottle capacity when it is full. IE A 10# with a tare weight of 13.8 would be full at, or around, 23.8.

Second question would be, assuming all the above is right... I know the pressure can vary by temperature but does that affect the weight?

Either way though you take an empty bottle to someone and they fill it and it should be as much heavier as the capacity of the bottle right?

OK that rambled but I just spent a frustrating day dealing with a keg store that though they have an awesome selection of beers has no clue about CO2, lol. The kicker was the third trip there was at 8pm and they are located a couple blocks from a college... you do the math. Oh and I hit a sobriety check point on the way home... not a big deal as I hadn't had anything yet tonight but it did mean close to 30 minutes sitting in cop generated traffic.

#### jaobrien6

##### Well-Known Member
CO2 is measured in weight... not PSI, not some other funky unit. Simple weight. The bottle is at its tare weight (stamped on the bottle as TW) when it is empty and at tare weight plus bottle capacity when it is full. IE A 10# with a tare weight of 13.8 would be full at, or around, 23.8.
Right.

Second question would be, assuming all the above is right... I know the pressure can vary by temperature but does that affect the weight?
Nope.

Either way though you take an empty bottle to someone and they fill it and it should be as much heavier as the capacity of the bottle right?
Yup.

You've got it all right, it's pretty simple and straightforward. As to why you're having troubles getting a good fill, that's tough to say. I can't understand how you could end up with a cylinder that only weighs 2 lb more than the tare weight after getting it filled. They're either completely inept or completely crooked. I can't think of another explanation.

#### prosper

##### Well-Known Member
that's right. The same way propane is sold. 10lbs of propane means that the full tank will weigh 10lbs more than the empty tank.

OP

#### TomSD

##### Da Geek
Yeah I figured as much. The keg place just seemed to be incompetent. The first two times they tried to fill me from an empty bottle. The last time it was getting hit with CO2 as it came back cold and sweaty but they had no scale and no idea what they were doing so it came back nowhere near full.

Going to call and talk to the guy again tomorrow... he was all kinds of accommodating. Going just ask for a partial refund then go to one of their other stores to see if they have a better idea of what they are doing. For now though the two pounds is enough to get my soda force carbing and my beer back online so I can draw it.

#### kpr121

##### Well-Known Member
I have had similar experiences with 2 local beer distributors. I think what it comes down to is they are filling the tank from a larger tank (say 100-200 lbs). The key is they are distributing the co2 from the TOP of the tank. Therefore you only receive the amount of CO2 it takes to equalize between high pressure (their tank) to low pressure (yours). Once this pressure equalizes, the flow stops. From what I understand, the proper way to fill is to distribute from the bottom, ensuring that you are getting all liquid, even after the pressure equalizes. Gravity takes over at this point.

I was suspicious of my local guy after a few fillups only lasted 2-3 kegs. Asked him if he weighed it. No he replied. So I brought my scale. Turns out that time they had just gotten their 100 lb tank refilled, so my tank took 4 lbs. Previously I had weighed 1 or 2 lbs at home. Got to talking to the guy,and realized he just plain didn't know what he was talking about. So I copped a deal that eveyrtime I need to fill up I would just call and ask when they last reupped. I don't mind because they only charge me 7 bucks to refill,but I wonder if other people even realize they are being duped?

Edit: Just wanted to add that my wife just made fun of me/yelled at me for talking about CO2 at 7AM on a Saturday Morning while in bed (typed that on my Palm Pre, she didnt love the tap tap tapping of the keyboard). I told her I can go elsewhere if she wants. She told me to go start my brewday. I love her.

#### ahave

##### Well-Known Member
No one should be filling your tank 'from the top' of their tank. If you fill from the top you will only be getting compressed Co2. What you want is 10 lbs of liquid Co2, which comes from the bottom.

In Knoxville I found a place that would purge & fill my 5# tank for \$7, and yes they used the proper equipment to fill it with liquid.

I just moved to pittsburgh - where do you go to fill your tanks? Which one is filling it with the way you describe?

#### kpr121

##### Well-Known Member
No one should be filling your tank 'from the top' of their tank. If you fill from the top you will only be getting compressed Co2. What you want is 10 lbs of liquid Co2, which comes from the bottom.

In Knoxville I found a place that would purge & fill my 5# tank for \$7, and yes they used the proper equipment to fill it with liquid.

I just moved to pittsburgh - where do you go to fill your tanks? Which one is filling it with the way you describe?
Its Green Valley Beer Distributor in North Versailles that I'm talking about. He even let me in the backroom to see his setup. Unless there is some sort of dip tube down to the bottom of the tank, it definitely dispenses from the top.

I also had my tank filled at Save-Mor in Squirrel Hill, where it only weighed 2 lbs above tare.

#### ahave

##### Well-Known Member
Sweet, I work in West Mifflin and live off carson st. So Green Valley shouldn't be too far away for me. Thanks!

There should be a dip tube inside the CO2 that runs to the bottom to pull out the liquid Co2. I would imagine that is what the guy is using. 2# over tare sounds like he didn't let the bottle cool down enough before filling it up. (maybe)

Fun fact: If you would open the valve to the tank of liquid Co2 so that it was dispensing into the air - liquid Co2 would come out and then freeze, which would give you dry ice!

#### prosper

##### Well-Known Member
'fill' tanks usually have dip-tubes in them, or are used inverted. To get a proper fill, you often have to chill your empty tank, too. Otherwise, the pressure in the two tanks can equalize stopping any further flow, before you've gotten your fill weight. The easiest way to chill your tank is to partially fill it, then vent it immediately. The rapid decompression will frost up the tank pretty damn quick.

To those places that are 'filling' tanks without the proper know-how: yikes! Under-fillinf is one thing, but over-filling a tank can be extremely dangerous! You absolutely MUST use a scale to know that you're not overfilling it.

#### kirscp

##### Well-Known Member
And sometimes they just don't pay attention. I took in a tank that the last hydro test was in 96. I told them I wanted that tank back and did not want an exchange, also told them it needed to be hydro tested, well when it came back, no new date stamped. They sent it off, but it only got refilled. The guy said he wouldn't charge me for the hydro test, since it wasn't stamped ... well, duh. I wouldn't have paid for it, as next time it comes in it'll need to get tested.