I have not seen any one who claims that Imam Ali's house water is bitter. Nevertheless, even if some claims that, it does not harm the sacred status of the place. The location of the house is near the river of Furat. Sometimes the water level in the river is high and sometimes it is low or even very low. That can be a possible reason of change in the taste of the water. It is worth mentioning that the house was never owned by Imam Ali (AS) but by his nephew (Jo'dah ibn Hubairah جعدة بن هبيرة)and Imam Ali (AS) was just a temporary tenant in that house.