Massachusetts Plumbers Journeyman Practice Exam

When connecting piping to cast iron soil pipe hubs, what materials should be used?

1. A. Silicone only

2. B. One-inch of molten lead

3. C. Cement

4. D. Duct tape

The correct answer is: B. One-inch of molten lead

When connecting piping to cast iron soil pipe hubs, using one inch of molten lead is the preferred method due to its effectiveness in creating a strong, leak-proof seal. Molten lead has been a traditional material for this type of connection because it expands upon cooling, filling any gaps and ensuring a tight fit that can withstand the pressure and movement associated with plumbing systems. This method is durable and long-lasting, especially suitable for cast iron, which is known for its strength and resistance to corrosion. Other materials listed have limitations or are inappropriate for this application. Silicone, for instance, may provide a temporary seal but lacks the structural integrity and durability required for long-term use in plumbing systems handling waste. Cement can also be utilized in certain situations but is not commonly applied to cast iron connections specifically. Duct tape is not suitable for plumbing applications due to its inability to withstand the conditions present in high-pressure or moisture-rich environments.