Sodastream cylinder for drysuit inflation?

[Mobulai]

Due to my partner’s Sodastream habit, I find myself with access to a lot of functionally free, within-hydro Sodastream cylinders. They’re a little longer and thinner than the typical AL6, with a service pressure of 250 bar and an internal volume of 0.6ish litres, giving them ~5 cubic feet of ‘free air’, which should be plenty for a single T1 dive.

The cylinder threads are M18 x 1.5, which seems to be the same as cylinders used for rebreathers in Europe. I can quite easily find valves for M18 -> DIN online.

Before I throw away $45 on a valve, does anyone have any thoughts/experience using these as suit inflation bottles?

about a year ago I had that same thought; but due to the lack of knowledge on my part about tank testing I kinda shelved the idea.
Also had also my worries about CO2 earing away quicker at the cylinder.

I want to use it to just workbench a diy ccr, and if things move forward I actually get the right tanks for the job.

Yeah which makes them 3-3.5cf. In theory just barely enough for a modest square profile T1 dive. Plan on it running out just when you want that tiny bit more loft in your suit at 9m

now I woulkd be more concerned about that working pressure thing.

@rjack321 nice signature btw

 

[ChrisMBC]

Before doing anything with these cylinders are you sure the 250 bar is the working pressure (eg indicated by PW250BAR) and not the test pressure (PH250BAR). The pressure of CO2 at room temperature only reaches around 60 bar before it turns to a solid. If the test pressure of the cylinder is 250 bar, working pressure is likely to be around 2/3 that (depending on the applicable standard), ie 167 bar.

You're very correct. I assumed that (like scuba tanks) the pressure written on the cylinder was the working pressure, not test pressure! At 170 bar, it's not really useful for anything except rinsing regulators...