Tank size and time available

[Lord Northern]

Heh, I see. Well it looks like predicting such a thing in almost impossible and it all depends on many factors.
But what's the maximum lenght? Like if I have double steel tanks and so on? What's the longest a diver can stay underwater?

 

[Dive-aholic]

Without doing the calculatoins, I'd guess I can hover motionless in 10 feet of water in a set of double 85s pumped up to 3600psi for at least 15 hours, probably longer. A cave dive in the same tanks pumped to the same pressure in a high flow system with an average depth of 93' my actual backgas dive time lasts about 70 minutes. But I also have about 1800psi left in the tanks at the end of the dive. So I guess you could double that if I were to just breathe them down to zero.