I wonder why no one has made an open source Soda stream that connects to the big tanks right out of the box in a thoughtful way. Or better yet, a system for refilling the sodastream tanks from a large canister so that the sodastream can still sit easily in your counter.
You can get Co2 tank and parts from beer supply company.
https://www.morebeer.com/category/co2-tanks-regulators-parts...
plenty YT videos on how to put them together.
They are absolutely massive. The tank that holds 13kg itself weighs about 30kg. So the amount of force to 'dent' that amount of steel would need to be ridiculous.
The weakest part is (by design) the valve. Technically I rent the bottle and buy the gas. Each refill is an exchange of the bottle after which the bottle gets pressure tested, etc.
I also added a standard regulator to my setup because I trust it more than the sodastream, tho the pressure rating of the sodastream should be enough.
Then I got a tank of food-grade co2 from my local supplier. I guess welding grade co2 would be good enough as well, but as the price difference was non-existent it was a no-brainer.
When you get a regulator, make sure you get the highest flow-rate you can find as some of them will be problematic to get enough pressure for your beverage.
Mine does not go nowhere as high as the regular sodastream bottles directly, but the result is that it takes me an extra 10 seconds per bottle to get the same result.
[0] - https://www.co2supermarket.co.uk/adapters-for-co2-regulators...