Final answer:
Water dripping from discharge piping in a hydronic heating system is most likely due to boiler scale formation. Hard water with calcium bicarbonate can result in insoluble calcium carbonate deposits as the water is heated, increasing pressure and leading to leaks.
Step-by-step explanation:
If water is dripping from discharge piping in a hydronic heating system, the most likely cause could be the formation of deposits known as boiler scale. Hydronic heating systems operate by circulating hot water, which can lead to the build-up of scale due to the chemistry of the water involved. Specifically, hard water contains dissolved calcium bicarbonate which is quite soluble. However, as water is heated and there is a loss of dissolved CO₂, calcium bicarbonate can precipitate out as calcium carbonate, which is quite insoluble.
This leads to the formation of scale within the piping, which can restrict water flow and cause an increase in pressure. This increased pressure can ultimately lead to leaks or dripping at points in the piping where the integrity may be compromised, such as joints and valves. Regular maintenance to address hard water and the potential accumulation of scale is essential to prevent such issues. If scale buildup is allowed to go unchecked, it can significantly decrease the capacity and efficiency of the hot water pipes in the heating system.