Riser clamps are being set on a vertical copper water line in a building whose floor-to-floor height exceeds the tabulated support interval. What is the greatest distance the support table permits between supports on vertical copper tubing?
- AAt each floor level only, with no maximum interval stated
Support at each floor is the common practice but it is not the rule as written. Where a floor-to-floor height exceeds the tabulated interval, an intermediate support is required.
- B4 feet
Four feet appears in the horizontal column for several plastics. Vertical intervals are longer than horizontal intervals for every material in the table.
- C15 feet
Fifteen feet is the vertical interval for steel pipe. Steel and copper are neighboring rows and the vertical numbers are the ones candidates swap most often.
- 10 feet
Why D is correct
The support table gives copper tubing a maximum vertical support interval of 10 feet. On a normal residential or office floor-to-floor height one riser clamp per floor satisfies that, but in tall floor-to-floor spaces an intermediate support is required to stay within the interval.
What this question is testing
The item tests the candidate's ability to use the vertical column of the support table by material and to recognize that per-floor support is a practice rather than the tabulated requirement.
On the job
Riser clamps do more than hold weight. They keep the stack from moving when a valve slams, and on hot water risers they set where the thermal growth goes, which is why you plan the clamp locations together with the offsets or expansion loops. Put the clamp on solid structure, not on a piece of blocking screwed to drywall, and check that the clamp material is compatible with the tube so you do not build a corrosion cell in a chase nobody will open for thirty years.
Memory technique
Copper stands ten feet, steel stands fifteen.
Exam tip
The support table has two columns. Read horizontal or vertical first, then find the material row.
Where to look it up
Chapter 3, Section 308 and Table 308.5, the vertical support column. Support intervals differ between IPC and UPC, so confirm against the code your state adopted.