text: such thing as de-ionised water? there should be no such thing as de-ionised water. if there are no ions in the water (including h and oh ions) how can there be a ph if the ph of de-ionised water is 7? you are right, you can not completely remove all the ions from water.  the equilibrium of water would just form more h+ or oh- as soon as you remove them. di water is a reference to the fact that it doesn't contain ions other than h+ and oh-.