Get a second opinion on the "head hala hua hai" part
When it comes to coolant its concentration is the key element. Too much and it would start to corode internal surface. Too little and theres no point of it (as advised by paksuzuki engineers).
There is no harm in using ac water as a replacement. Just make sure it is at room temperature when poured in. Also would suggest that you get the entire system flushed and cleaned to make sure all the corrosion/rust is out. Then pour in fresh water.