This is a question I have been asked often by patients. Often, they have been approached by salesmen of some alkaline water systems to buy a machine to alkalise water. So do we need to drink alkaline water? Some systems allkalise water to run at a pH of 9 for drinking.
Let’s go back basic physiology. Our blood runs at a pH of 7.35-7.40 (mildly alkaline), BUT our stomach runs at a pH of 1.5-3.5 (acidic), our small intestines and large intestines range in pH of 5.5 to 7 (mildly acidic to neutral). Our stomach needs to run in that acidic pH range in order to breakdown proteins. When the stomach acidity is compromised, there is delayed breakdown of food and rotting begins. (you are now thinking about overacidity, that is lactic acid from fermentation, not hydrochloric acid which we need for proper breakdown of proteins!)
So if you drink alkaline water at a pH of 9, it will start to neutralise your hydrogen ions from your hydrochloric acid (which you need) in your stomach and bring stomach pH to a less acidic level (bad for your digestion, slows it down, decreases absorption of minerals that need an acidic medium like calcium and magnesium, and increase gas from fermentation). Not a good idea at all. There is a distinction between body (blood) pH and stomach pH. If you truly want to alkalise yourself, drink lemon in water, make sure your mineral intake is adequate and eat plenty of vegetables and some fruits.
So the conclusion is: You should just drink filtered water. Invest in a good water filter and keep yourself hydrated! You don’t need fanciful alkaline water machines.