A branch carries 55 water supply fixture units. The demand table published for this project lists 50 units at 24 gallons per minute and 60 units at 27 gallons per minute, with no row in between. The design procedure for this project directs that where a fixture unit total falls between published rows, the next higher row is used. What demand sizes the branch?
- AA design demand of 24 gallons per minute
- A design demand of 27 gallons per minute
- CA design demand of 25.5 gallons per minute
- DA design demand of 55 gallons per minute
Where to look it up
Explicit exercise assumptions; not a universal code requirement.
Why B is correct
The stated project procedure requires the next higher table row. Since 55 fixture units lies between 50 and 60, use the 60-unit row: 27 gallons per minute. Linear interpolation would give 24 + (55 - 50) / (60 - 50) × (27 - 24) = 25.5 GPM, but this project does not permit that method. The two table entries alone do not establish the curve’s shape or whether interpolation is permitted elsewhere. Fixture units are a demand index, not GPM.