A frost-proof hose bibb is being roughed in on the exterior wall of a commercial building. Under the IPC table of minimum fixture supply pipe sizes, what is the smallest nominal supply permitted to serve that hose connection?
- A3/8 inch nominal
Three eighths is the table minimum for low-flow connections such as a flush tank. A hose connection carries several times that demand.
- 1/2 inch nominal
- C3/4 inch nominal
Three quarters is a sensible size for a long run or for a wall hydrant serving a wash-down, but the table does not require it as the minimum.
- D1 inch nominal
One inch is the minimum listed for a flushometer valve water closet, not for a hose connection. Carrying that number across rows overstates the requirement.
Why B is correct
A hose bibb is expected to supply a garden hose at a usable rate, so the table assigns it a half inch nominal minimum. Anything smaller would throttle the outlet before the hose ever got a chance to.
What this question is testing
Whether the candidate can locate the minimum fixture supply table and read the hose connection row without confusing it with adjacent fixture rows.
On the job
On commercial work the practical question is not the code minimum but the length of the run: a half inch line feeding a hose bibb sixty feet from the riser will disappoint anyone trying to fill a mop bucket. Contractors routinely run three quarter inch to hose bibbs and wall hydrants for that reason. Knowing the code floor tells you when an existing half inch stub can stay and when the complaint you were called about is a sizing problem rather than a code violation.
Memory technique
Half inch feeds the hose, an inch feeds the flushometer.
Exam tip
Memorize the shape of the fixture supply table rather than every number: small for tank fills, half inch for most fixtures, an inch for flushometers.
Where to look it up
IPC Chapter 6, Table 604.5, minimum sizes of fixture water supply pipes. The UPC publishes its own fixture supply table, so verify the entry in your adopted code.