Tile Lined Steel Sump - Deflection Limit?

[sdz]

I am designing a steel sump which is to have ceramic tile lining with epoxy adhesive. The sump is about 4m square x 4m deep (13'x13'x13').

What deflection limit should the walls of the sump be designed for? The tile supplier (Cumi) seems to not know.

Is L/500 stiff enough?

 

[Ron]

At most L/600...better if your constraints allow.