As there is no LEGO water pump available, I did this LEGO Technic compatible persitaltic water pump. Just print it, insert a flexible silicone tube, add some LEGO Technic wedge belt wheel, axles and bushes and you are done. Just need a motor, PF or Mindstorms ...

I used that pump in my LEGO Mindstorms DrinkBotDress serving cocktails during the Roboexotica 2016 festival for cocktail robotics! (in the pics you see the old yellow pump from aquarium supply, but that was too slow, so I printed my own!)