  The $K_S \to 3 \pi^0$ decay is a pure CP violating process which, assuming
CPT invariance, allows one to investigate direct CP violation. This decay has
not been observed so far, and the best upper limit on the branching ratio
$BR(K_S to 3\pi^0) < 1.2 \cdot 10^{-7}$ is two orders of magnitude larger than
predictions based on the Standard Model: $BR(K_S \to 3\pi^0) \sim 2 \cdot
10^{-9}$. In this article we present the search for the $K_S \to 3\pi^0$ decay
performed with the KLOE detector operating at the DAFNE {\Phi}-factory at the
Frascati Laboratory. We describe the analysis techniques used in the background
rejection and signal events selection as well as the evaluation of almost five
times lower upper limit on the $K_S \to 3\pi^0$ branching ratio. We discuss
shortly also the perspectives for a new measurement using the KLOE-2 apparatus
equipped with a new inner tracker and the calorimeters at low theta angle.
