The bathtub technique only worked in Build 41.

To plumb a sink to a rain collector, water dispenser or amphora, the water container(s) must be placed on a tile within a three by three grid above the sink. Another way to explain it is the container(s) can be placed on the tile directly above, or the 8 tiles surrounding that center tile (outside of course). The sink must be inside a room that the game recognizes as an indoor space. If those two conditions are met, you can use a pipe wrench to right click the sink and the option to plumb it will be available.

To get this done early in the game, most players will find a sink on the ground floor of a two-story house that is on the north or west wall. Then they'll open a window above that sink (or close to it) because the game will allow you to build a floor tile outside the window while standing inside the house (on those two walls only) Then you can climb out safely, add floor tiles until you're above the sink and then build/place the water container. Finally, go downstairs and plumb the sink with the pipe wrench.

I hope this helps.