While shutting off the burner as recommended above will help, it does not completely eliminate sludge and sediment from entering into your heating system. Another thing you can do to reduce the amount of contamination (sediment, sludge, and condensation) is to apply a treatment to your tank before each fuel delivery. Most hardware stores and home service centers sell home heating oil sludge and condensation treatments. You simply purchase the bottle and then pour its contents into your tank just prior to receiving your delivery. Many times customers leave the bottle by the tank with a note for the delivery person, asking them to add the contents to the tank before the delivery. Our drivers are always happy to do this.