ᐅ Installing water pipes underground

Hello everyone,
I want to install the water pipes in the floor of my new bathroom.
I have already removed the floor where my shower tray will go and found that there is screed, polystyrene insulation, and then the concrete slab below.

My question is, when I install both the shower tray and the pipes, what do I need to consider? I assume I need to seal everything again to prevent moisture from rising upwards, right?

Thanks for your help