Why barometric condenser leg height limit is 34 feet?

The barometric condenser leg height limit of 34 feet is primarily due to atmospheric pressure. At sea level, atmospheric pressure can support a column of Mercury approximately 34 feet high (or about 29.9 inches of mercury). When using water, the height limit is about 33.9 feet, as water is less dense than mercury. Beyond this height, the pressure difference becomes insufficient to maintain the column, leading to potential vacuum conditions and loss of condensate return.