A fuel water separator is a device that works to ensure clean fuel is delivered to the engine. In other words, a fuel water separator is a small filtering device used to remove the water from the diesel fuel before it reaches to the sensitive parts of the engine. Water and contaminants have a direct impact on the service life and performance of diesel engines. Nowadays, there are number of manufacturers who make fuel water separators with their concept of operation being common and only design variations being the major difference. The first stage of the fuel water separator uses a pleated paper element to change water particles into large enough droplets that will fall by gravity to a water sump at the bottom of the filter. The second stage is made of silicon-treated nylon that acts as a safety device to prevent small particles of water that avoid the first stage from passing into the engine. To remove the water from the fuel water separator the operator should periodically check the fuel water separator and open the valve to drain the water. A fuel water separator is a very important part of the fuel system.