Pipe and fittings in PVC and PPR, roof tanks, pumps and pressure sets, soil and waste, and the drainage runs out to the connection.
Everything is pressure tested before it is closed up and the test is recorded with a date and a name. A first fix signed off that way is the difference between a leak found on a Tuesday and a leak found after the tiler has finished.
We size the tanks and the pump for how the building will actually be used rather than for the floor area. A guesthouse with eight showers running at seven in the morning is a different building from a house with the same number of taps.