What is the result of water in the fuel-oil?

Water in fuel oil primarily results in incorrect atomization during the combustion process. When water is present, it interferes with the mixture of fuel and air, which is critical for efficient combustion. Fuel oil is designed to burn in a specific droplet size, and the presence of water alters the properties of the fuel, leading to larger droplets. This disruption can cause incomplete combustion, resulting in a higher level of pollutants and reduced efficiency in the heating system.

Since the proper atomization is necessary for a clean and effective burn, water's presence ultimately hinders the oil burner’s ability to function optimally. This can lead to issues such as increased smoke production and reduced heating performance. Hence, the correct answer acknowledges the detrimental impact of water in fuel oil on atomization, leading to inefficient burner operation.