PH of water how important is this

I am trying understand the need for PH balance in my diet. A company Young life http://www.lifeionizers.com/compare-all-ionizers.html sells filter systems for several thousand dollars that outputs water at a PH level 10 saying that our unbalanced diet requires that we have much more alkaline water. The also recommend eating lots of vegetables which helps keep the diet more alkaline. There is also a body of thinking that says dairy should be eliminated because it increases acidity.

This is good but the think I am confused about is the PH of water. I tested the water I have been drinking from a big remote lake in Canada for the last 5 months and the PH is closer to 5.75. This lake has incredibly healthy fish population and loon are mating and we see baby loons. The weeds are doing well. So I am confused because a big pitch of young life is to say that we need to go back to nature and the our city water supplies are so off that we need to drink very alkaline water. This is a big difference and with so much water going into your system I am wondering if there is any scientific bases or research behind their claims or the claims in general to make your diet as alkaline as possible. Certainly I am concerned about high fat dairy or the fat in meat but previously I had not been concerned that they are acidic?