Replacing the oil filter is the best routine maintenance you can do for your hot water or steam heating system.
Surround the base of the boil er with a drop cloth and newspaper. Shut off the power to the boiler at the main service panel and at the boiler shutoff switch, usually located near the boiler. Then, close the fuel line supply valve and wait 30 minutes for all parts to cool.
Wearing disposable gloves, unscrew the top of the filter cartridge. Remove the cartridge with a twisting motion and turn it over to dump the old filter into a plastic bag. Remove the gasket from the cartridge and wipe out the inside, first with a cloth dipped in solvent, then with a dry cloth. Install a new filter and gasket. Position the cartridge under the cover and screw it back in place.
Use an open-end wrench to remove the bolts from the pump cover. Leave the oil line attached, and remove the gasket and mesh strainer from the cover. Clean the strainer with solvent and a parts
brush. If it’s badly worn or damaged, replace it. Wipe the cover with a clean cloth. Place the clean strainer or replacement strainer in the cover and install a new gasket. Fasten the cover bolts in place. Restart the boiler.