You can use tap water, but distilled is much better, (no minerals or cantaminants, chlorine, etc.,). Mix it 50/50 for best cooling properties.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed