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Practice question · NEC 250.104(A)
What Size Bonding Jumper for Metal Water Pipe?
Exam-style question (Sparky QOTD)
Metal water piping in a building is bonded per 250.104(A) with a bonding jumper sized per:
A. Table 250.102(C)(1)
B. Table 250.66
C. The same size as the water pipe
D. Table 250.122
Answer: A) Table 250.102(C)(1).
Where to Find It
Open your Code book to 250.104(A) — it sends you to Table 250.102(C)(1) for the bonding jumper size. Two hops: the section names the job, the table gives the size.
Why This Table
Article 250 has three different sizing tables for three different jobs, and the exam mixes them on purpose: Table 250.66 sizes grounding electrode conductors, Table 250.122 sizes equipment grounding conductors, and Table 250.102(C)(1) sizes bonding jumpers. Interior metal piping gets a bonding jumper — so it's the bonding-jumper table. Match the noun to the table and you'll never miss one of these.
The Trap
Choice B (Table 250.66) is the most-picked wrong answer because 250.66 is the famous one — the GEC table everyone memorizes first. But a water-pipe bonding jumper isn't a grounding electrode conductor. Different job, different table.
Exam Tip
When you see “bonding jumper” in a question, your finger should go to 250.102 before you finish reading the sentence.
Keep Drilling
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