I have a outside woodburner boiler tied into my oil fired boiler in my home. With winter coming to an end. I will be shuting down my wood burner, I would like to shutdown my oil boiler also. Can I simply just shut them down or do I need to drain the whole system? I don't want to run the boiler just just to maintain a boiler temp. I am worried the oil boiler might rust, my wood burner is made of stainless steel. I installed it two years ago and added a anti-rust agent then. Any suggestions?