Hii dear ! first of all take away the myth of water change from your mind. Eat a protein rich diet daily like egg,soyabeen,pulses,paneer .This is so because our hair are made of proteins.. so to have good hair eat lots of proteins.. you can also take hair vitamins under supervision of a dermatologist.

hi,
hair fall could be due to change in water no doubt. but since you have dandruff plus hair fall it goes in favor of fungal infection of hair, which is very common. but before using anti fungal shampoo , you should try this method to reduce dandruff an hair fall
for dandruff - use your regular shampoo daily for 2 weeks, alternate days for 2 weeks,weekly twice for 2 weeks. follow this pattern and you will surly see reduction in dandruff. if not you have to use anti fungal shampoo after consulting dermatologist .
for hair fall- stop using hot water , hair dryer, wear scarf an use helmet wear helmet.then increase protein intake 1 egg plus a glass of milk daily, correct anemia if present, take a multivitamin containing biotin. try these it does not help you have use minoxidil for hair fall under supervisionb of dermatologist.
thank you
dr.mukesh