Nobody has mentioned not drinking tap water! And I don't know what kind of gym you go to but I have never in my life known anyone drink that amount of milk and consider themselves healthy, and I go to the gym, pool and various fitness classes.
As has been mentioned before, by drinking four pints of full fat milk you are taking on way too much fat per day, the natural recurring sugars found in milk are also very damaging to your teeth, despite having high amounts of calcium making your bones stronger. You could obtain this calcium from a hundred other cources including yoghurt, cheese and other dairy products, and some fortified products like orange juice, bread and soy milk.
The FDA recommends that an adult should not consume more than 65grams fat per day (this equates to 585cals). By drinking four pints of full fat milk you are consuming 88grams of fat per day without having actually eaten anything solid or good for you! Your heart must be furry :-(
You sound like you know better anyway, but as Ethel already pointed out. There is actually no need for adults to drink milk at all.