  Context. Our Galaxy is composed of different stellar populations with varying
chemical abundances, which are thought to imprint the composition of planet
building blocks (PBBs). As such, the properties of stars should affect the
properties of planets and small bodies formed in their systems. In this
context, high-resolution spectroscopic surveys open a window into the chemical
links between and their host stars.
  Aims. We aim to determine the PBB composition trends for various stellar
populations across the Galaxy by comparing the two large spectroscopic surveys
APOGEE and GALAH. We assess the reliability of the PBB composition as
determined with these surveys with a propagation error study.
  Methods. Stellar spectroscopic abundances from the large surveys GALAH-DR3
and APOGEE-DR17 were used as input with a stoichiometric condensation model. We
classified stars into different Galactic components and we quantified the PBB
composition trends as a function of [Fe/H]. We also analysed the distribution
composition patterns in the [$\alpha$/Fe]-[Fe/H] diagram.
  Results. Our propagation error study suggests that the overall trends with
[Fe/H] and [$\alpha$/Fe] are robust, which is supported by the double study of
both APOGEE and GALAH. We therefore confirm the existence of a bimodal PBB
composition separating the thin disc stars from the thick disc stars.
Furthermore, we confirm that the stoichiometric water PBB content is
anti-correlated with [Fe/H].
  Conclusions. Our results imply that metal-poor stars both in the thin and
thick disks are suitable hosts for water-rich PBBs and for ice-rich small
bodies. However, for metal-poor stars ([Fe/H]<0), the PBBs around thick disc
stars should have a higher water content than that around thin disc stars
because of the $\alpha$-contentdependence of the water mass fraction.
