All water services 1 through 1 1/4 inches shall be type ________________ copper.

The correct answer is type K copper, which is often required for various plumbing applications, particularly those involving water service lines. Type K copper has the thickest walls compared to other copper types, making it extremely durable and suitable for underground installations prone to high pressure and potential damage from external factors. This added thickness also provides enhanced resistance to corrosion, which is critical for maintaining the integrity of water service lines over time.

In many plumbing codes, including the Omaha Plumbing Code, the selection of copper types is guided by factors like pressure, temperature, and environmental conditions. Type K copper is ideal for water services ranging from 1 to 1 1/4 inches due to its robustness and longevity, ensuring a reliable supply of potable water.

Other types of copper, such as L, M, and N, have thinner walls and may not be suitable for the rigorous demands of a water service line as defined in the plumbing code. Therefore, the specification of type K copper supports both safety and compliance with local plumbing regulations.