Journeyman Plumber ExamWater Supply SystemsEasy
A plumber is sizing a hot water distribution system for a multi-family residential building. The design calls for a continuous supply of hot water to multiple fixtures simultaneously. Which of the following is a primary factor that influences the required flow rate (GPM) for sizing the hot water distribution piping?
- AThe length of the water service line from the street main.
- BThe total number of cold water fixtures in the building.
- CThe material of the hot water storage tank.
- DThe specific type and number of hot water-consuming fixtures.
Show answer & explanationAnswer & explanation
Correct answer: D. The specific type and number of hot water-consuming fixtures.
The required flow rate (GPM) for hot water distribution piping is primarily determined by the specific type and number of hot water-consuming fixtures. Each fixture has a specific demand (e.g., lavatory, shower, washing machine), and the sum of these demands (using demand factors) dictates the overall flow rate necessary for proper sizing.
Why the other options are wrong
- A. The length of the water service line primarily affects overall pressure loss and the sizing of the main service line, not specifically the hot water distribution GPM.
- B. Cold water fixtures do not directly impact the sizing of hot water distribution piping.
- C. The material of the hot water storage tank affects durability and heat retention, but not the required flow rate for the distribution piping.
Hot Water Piping Sizing Factors
Sizing hot water distribution piping involves calculating the anticipated flow rate based on fixture demand, pressure loss, and velocity limits to ensure adequate supply.
- Fixture units or GPM demand for each hot water fixture.
- Simultaneous demand (demand factors) for multiple fixtures.
- Available pressure, pipe length, and material also influence sizing.
Memory trick: Fixtures Fuel the Flow, Sizing Follows.