Personaly i keep mine @ a ph reading of anything between 5.8-6.2.I've had the best results from keeping the ph @ this level.But u have to keep in mind what the water is like in your area, if its chalky and ur kettle is limescaled up then its hard water meaning its slightly acidic.The water in my area b4 i've adjusted it is about the 7.0-72.ph.