SodaStream is at home water carbonator. It uses (smallish) 410g CO2 bottles. I have a large 20 lb CO2 tank and adapter that I used to refill my bottles.
For 99.9% of owners they have to ship it back to SodaStream (or a third party) to receive a refilled one. The cost is around $15-20 per refill. It costs me maybe $.50 to refill it with my large tank and takes about one minute. I own six small 410g bottles. So what I’m thinking is someone messages that they’d like to do a refill, then drives to my house and gives me their empties and I hand them fulls. I understand I’d be giving out my address to the public but it’s a small town and I would be direct messaging them it (not posting it). I could also offer to drive and drop off bottles for a fee. I work remote so I could do this 7 days a week.
Is this a reasonable (very) small hustle? Even 5 bottle would be $47.50 profit per week. The only issue I can think of is that if I give someone a bottle and they somehow managed to rupture it and injure themselves, with either the cold gas/liquid or metal fragments, they could go after me. But it seems other companies don’t consider that a significant risk as they ship them all the time. If there is enough interest and it’s continuous business, I could start an LLC and look into some type of broad umbrella insurance.
Are you filling by weight? Are the bottles you’re filling actually FULL, or do they just have some pressurized gas in them?
The fill time you’re describing implies you’re just putting some gaseous co2 in the bottle and likely not actually filling it. The bottles have an empty weight (will be stamped TW or tare weight) on the bottle. A quick search says a full bottle will have 410g of co2 (a little less than a pound).
If your “full” bottles actually weigh 410g more than your empty ones, you’re doing a great job. If they’re substantially less than that, you are selling partially full bottles.
A local shop here fills them - they have a special mother tank with a dip tube that goes to the bottom so it’s pulling liquid co2. They fill the bottle, then vent it all out again to get it super cold, then fill it again. That method gets pretty close to a full bottle, they’re usually 90% of their full weight.
I know what I’m doing, but you are right to be concerned. It can be tricky to fill them not only because they need to be filled with liquid not gas but also because SodaStream has this weird type of proprietary “anti-fill” cap on them, and if CO2 flows into them too rapidly it locks out the bottle. So to do this effectively, you not only need the adapter but also a throttleable valve, more finely throttleable than the main tank valve.
I don’t have my numbers in front of me so I am making up these numbers, but essentially the process starts with a bottle’s overnight stay in the freezer. If you don’t chill them down ahead of time, you can’t fill them to full capacity. Then they go on the hanging scale with the adapter on, empty the weight is something like 1040g (which is the bottle + adapter). Then I fill them to 1440g (which is bottle plus adapter + 400g CO2). I always fill to 400g of CO2 instead of 410g to play it safe. So I leave off the last 10g. I’m not sure how I would trip it but I want to avoid possibly popping the bottle’s rupture disc, maybe if they’re left in the sun all day?
My tank does have that dip tube, it’s called a “siphon tube” and it ensures that I pull liquid from the large tank. I’ve been doing this for years - I can feel the weight and the change in CO2 filling flow by hand this point. My scale’s battery died at one point and so I was ballparking it. After later replacing the batteries, I weighed a few of my filled tanks and I was within 25-50g (and I intentionally slightly underfilled them to play it safe).
When I started this it took a couple minutes for each bottle but now I have it down to a science, how much I can throttle fill without tripping the anti-flow valve.
I 100% approve of your methods and support what you’re doing!