PLA and air pressure. Any advice on thickness for ~100 psi

[curious aardvark]

100psi - Hmm.
What shape is the tank going to be and what orientation are you going to print it in.
A rectangle with a hollow interior could work as you culd print it lying down and then wrap it in some really shit hot sticky tape.
I can't see it holding pressure unless you seal it or wrap it in fibreglass resin, or something similiar.

In short - it's probably not going to work.

Black vinyl plumbers tape could work.
It self anneals and if you wrap it with stretch, it exerts a decent amount of compression.
So print the tanl. Wrap it in a couple layers of stretched black vinyl plumbers tape (other coklours are available) then seal it with some kind of paint on resin.

If it still blows up - it's not my fault :-)

[Mvago]

That is great to know What about using resin material for that? Will the object printed on a resin 3D printer be able to hold that? Is resin stronger? I also have access to a resin printer, if that is better I can try on that one.