Written by Gary Ikari
The subject for this month is plumbing fixture count based on the occupant building load. I shall discuss how you determine the code minimum plumbing fixture amounts. These values are based on the type of occupancy and the amount of occupants. The plumbing fixture amounts should be coordinated with the architect as the amounts directly affect the architecture layout. Plus, it is nice to flush out any major issues as earliest time as possible.
First, verify the occupancy for the space. This is typically completed by the architect. The occupant type also determines the amount of occupants.
Secondly, once the occupant type and amount of occupants have been determined, the breakdown of male and female is fifty (50%) percent of the total occupant load is the amount used for male and female. I.e. 268 total occupants / 50% = 134 male and 134 female.
Next, obtain the appropriate plumbing code and year that the project will be permitted. This discussion will use the California Code of Regulations Title 24, Part 5 – California Plumbing Code. With the above information, locate Table 4-1 (or Table 4-2 if the project is an OSHPD 1, 2, 3, or 4 project). The table is broken down into columns identifying the occupancy type and plumbing fixture types. Locate the occupancy type that the architect determined on the first column. Apply the male and female occupants for each type of plumbing fixtures to determine the quantities. If the values exceed the prescribed range, an additional fixture will be required for a stated amount of persons.
Lastly, confirm the plumbing fixture quantities that were determined from the method above with the California Code of Regulations Title 24, Part 2 – California Building Code. The tables are very similar but may have minor discrepancies. The discrepancies are the items that should be brought to the architect’s attention. This could be the item that holds up a permit during the plan check process. Since we (Plumbing Engineers / Designers) are the experts with all things plumbing, doing the due diligence of back checking the plumbing fixture quantities may save many headaches and heartaches when you believe the project is almost at the point of obtaining a permit.