Too much of anything kills. Lemon water is very powerful, especially on it's own. For some, it is never recommended by itself and I would suspect that if combined with distilled water over an extended period of time that it may cause harm. However, if taken in proper proportions with the other needed minerals and carbons you will greatly benefit.
I still drink my moreless "alkalizing" drink, but need just a small amount just once a day. My health has never been better! It did take me some time to get my body back in balance, but it was worth my efforts to keep at it.