Definition - What does Demi Water mean?
Demi water is an abbreviated name for demineralized water, which is water that has had all minerals, salts and ions removed.
Demi water is also known as demineralized water.
Corrosionpedia explains Demi Water
Demi water is useful for applications where water with low salt and conductivity properties are required. Due to the significantly low rate of conductivity, demi water is ideal for use in metallic equipment applications that are prone to corrosion. The lack of ions prevent oxygen from reacting with the metal surface to form corrosion or rust.
Understanding Corrosion in Pumps and How to Deal With It