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I dont know, I add water maybe once every 2 to 3 months. I cant even tell you the last time that I needed to fill the tub. Im not saying anything is wrong with your tub, I am just suprised with how many people need to fill their tubs on such a routine basis.
this just really seems odd to me. If I was adding water that much, I would be a little concerned. For the people that are out of the initial over useage of the tub, do you find that the amount of water that you add has gone down???