# Paintball co2 tank filling question



## Frozen (Mar 17, 2013)

Hi Everyone!

I bought a 24 oz paintball co2 tank. I took it to my local sports store to fill it up. It wasn't as heavy as i expected and it ran out quickly. So the next time I weighed my tank first and it was 2.2 lbs and then took it to the store. After it was filled it only weight 3 lbs.

I'm wondering if when they say 24oz if the mean by weight and i should expect the tank to be 3.7 lbs or by volume or something where it doesn't correlate to overall weight.

Thanks!
Frozen


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## wastewater (Apr 5, 2010)

Your scale showed 2.2lbs with an empty tank. What is the 'tare weight' that is stamped on the tank (TW is what the manufacturer says the tank weighs when empty)?

Maybe a couple of things are going on ~ the TW stamped on your cylinder is a different weight than what shows up on your scale; the refiller's scale is showing different readings compared to your scale; or the refiller is erring on the 'lighter' side to be safe. In theory, a 24oz paintball tank should be able to hold 24oz of liquid CO2 safely.


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## PhillyMurse (Mar 11, 2013)

How quickly did it run out?


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## All your base (Dec 6, 2006)

Typical process for filling a paintball tank is to connect it to the filling rig, bleed it empty, then put it on a scale and zero the scale before filling. Then, you fill until the scale is at the tank's capacity. In other words, you ignore the tare weight or what the tank weighted at home on a different scale.

I'd guess that either the store is (perhaps unintentionally) improperly filling your tank, or it wasn't totally empty when you brought it to them. Or one of the two scales in question is way off.


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## wastewater (Apr 5, 2010)

All your base said:


> In other words, you ignore the tare weight or what the tank weighted at home on a different scale.



I respectfully disagree.

The manufacturer's TW stamp gives a fairly accurate idea as to what the empty tank weighs. If the empty tank weighs 2.2 lbs on my scale, and the TW stamp says 1.5 lbs, I know my scale is probably off (or the empty tank is not really empty).

Let's say the TW stamp is indeed 2.2 lbs (or close to that figure) and I take my tank to be refilled (regardless of proper re-filling procedures) ~ I return home to weigh my refilled tank ~ which now shows 3 lbs on the scale ~ I now know the refill was not full capacity.


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## Frozen (Mar 17, 2013)

Thanks for all the responses!

To clear a few thinks up:

My scale showed empty weight as 2.2 lbs. (The tank was completely empty)
The manufacturer lists the weight online as 2.2 lbs
*I was not able to find the tare weight on my bottle I'll keep looking

I was expecting the filled capacity to be 3.7 lbs (2.2 + 1.5 (24 oz)). When I weighed the "filled" bottle it was only 3.0 lbs.

I went back to the store and told them that it was not filled all the way and asked them to fill it up. So they went in back and did what they could. The guy told me he placed 31 oz in the tank. It did feel heavier and when I got back home and weighted it the tank was 3.4 lbs. This was close enough for me.

Additionally, I tested my scale at home. I placed 4, 8, 10, 15 and 20 lbs dumbbells on it and the scale showed the correct weight exactly. This gives me some confidence in the calibration of my scale!

I would appreciate any comments


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## Manegy (Feb 13, 2012)

it was probably improperly filled the first time. to fill a CO2 tank you have to fill it with as much CO2 as it will hold(it will fill until the supply tank and your tank equalize in pressure) then release it all and fill it again. Releasing it quickly drops the temperature inside the tank which also drops the pressure. The pressure difference is what allows the tank to be filled to capacity.


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## All your base (Dec 6, 2006)

wastewater said:


> I respectfully disagree.


I don't think you need to disagree with me, since we are not providing conflicting information. 

Just to clarify, what I was trying to do was explain a typical fill procedure used on these containers. The procedure to ensure a full tank doesn't depend on tare weight or what it weighted on a customer's scale, it only depends on the relative weight between known-empty and cold (i.e. properly bled) and full. When I said "you ignore the tare weight or what the container weighted on a different scale at home" I was speaking about a typical fill procedure in the generic sense, not about this specific instance.


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## wastewater (Apr 5, 2010)

:wink:No problem... thanks for the clarification.


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## sarahspins (Sep 24, 2012)

Frozen said:


> So they went in back and did what they could. The guy told me he placed 31 oz in the tank. It did feel heavier and when I got back home and weighted it the tank was 3.4 lbs. This was close enough for me.


Did you mean 21oz, or did they actually say 31oz? 21oz makes more sense if you are saying the newly "full" tank weighed in at 3.4lbs.

When I've had my 24oz tanks filled they are generally about a half ounce shy of their fill weight... the place I get them filled always tells me how much they put in them. I think the most I've ever had one filled is 23.8oz


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## All your base (Dec 6, 2006)

First they're apparently underfilling it, then they're admitting to overfilling it (31 oz into a 24 oz tank)? I'd find a different shop. They're alternating between ripping you off and putting your safety at risk.


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## Bettatail (Feb 12, 2009)

All your base said:


> First they're apparently underfilling it, then they're admitting to overfilling it (31 oz into a 24 oz tank)? I'd find a different shop. They're alternating between ripping you off and putting your safety at risk.


+1.

there are couple guys work at the local sportsauthority and fill the paintball tank, I trust one of them, the other guy, I told him directly, no, don't touch my paintball tank.


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## Frozen (Mar 17, 2013)

sarahspins said:


> Did you mean 21oz, or did they actually say 31oz? 21oz makes more sense if you are saying the newly "full" tank weighed in at 3.4lbs.


He told me he put as much as he possibly could into the tank which according to him was 31 oz (no mistake). Based on how the tank felt in my hand I could tell it was more than before but not overfilled. When I got home I weighed it and the net co2 weight was 1.2 lbs. not the 1.5 lbs the tank should hold.

I think what Bettatail said make sense, was at a store similar to sports authority and I think from what people said on yelp and forums there is only one guy there who fills them correctly and he was not there that day.

Can someone confirmed this: Based on my knowledge of science and co2 I was under the impression that the tank couldn't be overfilled because they were filling it from a larger tank. The co2 pressure in both tanks would equalize at some point and they couldn't force more in past that. The only way to overfill is to have a higher pressure source which they did not.


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## Bettatail (Feb 12, 2009)

Frozen said:


> He told me he put as much as he possibly could into the tank which according to him was 31 oz (no mistake). Based on how the tank felt in my hand I could tell it was more than before but not overfilled. When I got home I weighed it and the net co2 weight was 1.2 lbs. not the 1.5 lbs the tank should hold.
> 
> I think what Bettatail said make sense, was at a store similar to sports authority and I think from what people said on yelp and forums there is only one guy there who fills them correctly and he was not there that day.
> 
> Can someone confirmed this: Based on my knowledge of science and co2 I was under the impression that the tank couldn't be overfilled because they were filling it from a larger tank. The co2 pressure in both tanks would equalize at some point and they couldn't force more in past that. The only way to overfill is to have a higher pressure source which they did not.


it is how much liquid co2 can fit in the space of the co2 tank, but there is must be empty volume for gas co2 so the pressure is around 800 max(under fill is 800 psi too), overfill the tank pressure is much more than the safety pressure.

there is a wonderful thread that hoppy made, explain the relationship of liquid co2 volume, tank pressure and temperature, you can use the search function to find this thread in this section, good read.


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