You probably should, as the copper coils where the heating is happening within the system certainly will hold water unless you have 'blown' out your lines, at least those connected to this water heater.
I'm not sure regular water heaters 'can't' accept the pink stuff, but since they are 'holding tanks', it's probably not a good idea since it will try to 'fill' the tank.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
100,000+mi since '14 - US, Alaska, Canada.... formerly Georgia, then NorthCarolina, now Alabama : )