What type of fitting may be required to connect potable water at a water heater?

The correct choice is the dielectric union, which is essential for connecting potable water at a water heater. A dielectric union serves a specific purpose in plumbing systems where different types of metals are joined together, such as copper and galvanized steel. This fitting helps to prevent galvanic corrosion, which can occur when two dissimilar metals come into contact with each other in the presence of an electrolyte, such as water.

Using a dielectric union allows for a non-conductive barrier between the two metals, thus preventing corrosion that can lead to leaks and system failures over time. This is especially important in the context of water heaters, where the hot water can exacerbate corrosion issues.

In contrast, while ball valves, compression fittings, and solder joints are common types of fittings used in plumbing, they do not mitigate the corrosion risks associated with connecting different metals. A ball valve serves as an on/off control and is not specifically designed to prevent corrosion. Compression fittings provide a secure connection but do not address metal compatibility. Solder joints are useful for joining copper pipes but also do not prevent corrosion when in contact with dissimilar metals. Hence, the selection of a dielectric union is crucial for maintaining a reliable and long-lasting connection in potable water systems, particularly at the water heater