The cost of water cooling at the fill station isn't incredible. Many shops use 55-gallon Rubbermaid trash containers, one tank per container, better than nothing. And since the tank can only lean over so far, if you don't overfill the container the valve stays dry too.
But it doesn't cost a fortune to build a "pool" out of concrete block or cinderblock and use that with multiple tanks and fills. There's some value in having a thick water jacket around the tanks, and a masonry wall around the water, because IF a tank bursts, all that water and masonry will help ensure that fragments only go up, rather than outward among the customers and employees.
Pardon me for speaking in PSI not Bar, I just never made the switch. But when an Alu80 is certified for use at 3000 psi with a 10% overfill, that means the shop can (arguably should) fill it to 3300 psi. And our hydro shops simply don't care but the tank can maintain that plus rating forever, so 3300 PSI should be no concern. The burst disc would routinely be around 4000 psi and the tanks are certified for use at 5000 psi (which is how they are retested at hydro) for 100,000 fill cycles. So again, using them at "new tank overfill" pressure is still plenty conservative.
I did hear one shop say they never filled over 3000 "because it works our compressor too hard" and that's just called shoddy equipment or a cheap owner. Regardless of the rated pressure in a tank, having or losing a 10% or 15% safety margin in the capacity given by the fill, is worth considering. With all the expense and effort consumed in diving, who wants to give up 10% of their sport time because some shop is too lazy to simply do a proper fill?
