When water meets metal, there’s a danger of corrosion starting. Corrosion is a chemical reaction between water and metal in the presence of oxygen, and the damage it causes to metal can quickly ruin many types of appliances as it weakens the metal until it starts to crumble away.
The water heater in your home is primarily made of metal and it stores and circulates water. So why doesn’t it start to rust? Corrosion is rare in water heaters, usually only starting late in the system’s life. there are several reasons for it.