No, your refreshing glass of water won't spontaneously combust. Water is made up of two elements, hydrogen and oxygen. Hydrogen is flammable, but oxygen is not. ... You can't burn pure water, which is why we use it to put out fires instead of starting them.

Is water a combustible substance?

Water does not burn in presence of air and oxygen. Hence , water is a not combustible substance.

Can water get set on fire?

Everyone knows that water is a readily available liquid that doesn't burn, and therefore puts out fire, but have you ever thought about why that's true? This doesn't happen…. normally. Water is made of hydrogen and oxygen atoms, and both of these elements support combustion.