When you leave an oil tank only partly full over the summer, you’re also leaving a pocket of air inside where water can condense. Moisture is all it takes for bacteria to build up and grow. After the bacteria dies, it falls to the bottom of your tank and helps create sludge – a leading cause of system breakdowns.

The condensed water can also corrode your tank and, if it gets into your heating system, it becomes another cause of breakdowns. By keeping your tank full of oil over the summer, you can help prevent these problems.