> then the water will condense and when they open it again the entire system will hammer, forever, until the building engineer drains it That's not true. I've

> then the water will condense and when they open it again the entire system will hammer, forever, until the building engineer drains it That's not true. I've had issues with my house steam system in the past where I added too much water to the furnace and draining the furnace did the trick. Any excess water will simply turn to steam and cycle itself out of the system.