What is the diameter of the drip leg for a steam main up to 6" NPS?

The diameter of the drip leg for a steam main up to 6" NPS is indeed the same as the main. This is due to the requirement for proper drainage of condensate; a drip leg must be capable of effectively capturing and removing condensate that accumulates in the steam line. By maintaining the same diameter as the steam main, you ensure that there are no restrictions that could impede the flow of condensate out of the system.

Using a smaller diameter could result in an increased risk of blockage or backpressure that could prevent effective drainage, leading to operational issues such as water hammer or reduced efficiency. Keeping the drip leg at the same diameter as the main promotes consistent flow dynamics and enhances the overall reliability of the steam system. The alternatives do not fulfill these requirements effectively, as they would introduce potential restrictions or insufficient capacity for condensate removal.