The soldered elbow at one end of the baseboard heating decided it wanted to start leaking today. 2 zone system, up and down. This is downstairs. Do I have to drain the boiler to repair this or will the zone just empty when I take the elbow out for repair and re solder. Do I have to shut the boiler off. How will the zone refill or how does the boiler refill. It is a Burnham ES2 boiler and most likely auto fills. I had to do a repair on this line 13 years ago, cut the line and used a sharkbite. It was on a straight piece. I might use a sharkbite for the elbow. I haven't decided yet. I have soldered fittings and done basic plumbing.