What is the maximum number of water closets with a fixture rating of 4 fu allowed on a 4 inch building drain with a 1/4 inch slope?

To determine the maximum number of water closets that can be connected to a 4-inch building drain with a fixture rating of 4 fixture units (fu) each, it is essential to refer to the plumbing code's calculations related to drainage system capacity.

Building drains are designed to handle a specific load defined in fixture units, which takes into account factors such as the size of the pipe, the slope, and the type of fixtures. In this scenario, the 4-inch drain must be assessed based on the total fixture unit load that it can safely accommodate.

According to plumbing code standards, a 4-inch building drain typically has a maximum capacity of approximately 40 fixture units. Since each water closet in this scenario is rated at 4 fixture units, the maximum number of water closets that the drain can support is calculated by dividing the total allowed fixture units by the rating of each water closet.

Thus, if the drain can accommodate 40 fixture units, and each water closet is rated at 4 fixture units, the calculation is as follows:

40 fixture units / 4 fixture units per water closet = 10 water closets.

However, this number is doubled to account for factors like peak loads and usage times, tipping the final allowance closer to the