Pure water (deionized) is actually really bad for cooling systems because it will slowly dissolve the metals it's in contact with. You definitely want Distilled water (organic content removed) usually mixed with a glycol to improve corrosion protection and lower the freezing temps, with the most common one being ethylene glycol which can contaminate food and drinking water and make it unsafe for consumption
Pure water (deionized) is actually really bad for cooling systems because it will slowly dissolve the metals it's in contact with. You definitely want Distilled water (organic content removed) usually mixed with a glycol to improve corrosion protection and lower the freezing temps, with the most common one being ethylene glycol which can contaminate food and drinking water and make it unsafe for consumption