Yes, I am sure. How does water differentiate between something you need like magnesium, and something you don't need like lead? Water does not have a brain to say I will take the bad stuff or the excess, and leave the good or what you need. It was water that carried the nutrients in to the body and it is water that is going to carry most of it out.
As for losing calcium, that is not quite true. For instance, calcium can be lost from bone due to an increased release of parathyroid hormone due to an excess or perceived high phosphorus level, or a low or perceived low calcium level. Calcium loss can also occur for other reasons such as lack of straining the bone. Bone is piezoelectric due to its silica content. The stress applied to bone during activity allows the bone to mineralize through electrodeposition. Therefore, when we fail to stress the bones the bones will demineralize. It has nothing to do with an acidic pH in this case.
In fact in my opinion the whole acid/alkaline thing is pretty much hype that keeps being spread in the name of sales. I don't think that half the people spreading this information have a clue how many ways the body has to maintain its proper pH. Even breathing affects pH. In fact if you want to alkalinize real fast all you have to do is hyperventilate. You will go really alkaline real fast, and you will also be flat on the floor for the same reason. This is why the body has so many redundant backups to maintain its pH. It does not require much of a shift to the high or low on pH before a person will start experiencing problems. This is also why both acidosis and alkalosis (a high alkalinity) are both considered serious problems.
If people really want to help their body maintain its proper pH then they should more mineral rich foods like vegetables and seaweeds. They can also drink spring water as well as breathe a little deeper.