What flow rate and flow pressure is used for determining peak demand of a bathtub at the point of outlet discharge?

• A. 2 gpm, 15 psi
• B. 4 gpm, 20 psi
• C. 5 gpm, 25 psi
• D. 6 gpm, 30 psi

Answer: (B)

Determining the peak demand of a bathtub at the point of outlet discharge involves understanding the typical flow rate and pressure necessary for effective operation. The chosen flow rate of 4 gallons per minute (gpm) at a pressure of 20 pounds per square inch (psi) is based on industry standards that reflect real-life usage scenarios.

A flow rate of 4 gpm is adequate for ensuring that water can fill the tub at a reasonable speed while also allowing for good performance during use, such as filling with warm water quickly enough for user comfort. The pressure of 20 psi is deemed sufficient for maintaining good flow without being excessive, which could lead to issues like splashing or rapid wear on plumbing fixtures.

These parameters are deemed practical for residential plumbing systems, considering the balance between adequate supply response and the physical capabilities of plumbing fixtures. In contrast, other options either do not align with typical standards or may overestimate the necessary flow or pressure without a clear justification.