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Materials, Joints & Supports — Plumber Practice Questions

55 questions · 12% of the Plumber exam

Worked questions

1. What limits the lead content of solder and flux used on joints in a potable water system?

  • ASolder may contain up to 2 percent lead where the water supply is treated to control leaching.
  • BLead content is unrestricted on lines smaller than 1 inch, because the wetted surface inside small tubing is too little to matter.
  • CLead is permitted in flux but prohibited in the solder itself, since flux burns off during heating and never contacts the water.
  • Solder and flux used on potable water piping must be lead free, containing not more than 0.2 percent lead

Where to look it up

https://www.ecfr.gov/current/title-40/chapter-I/subchapter-D/part-143/subpart-B/section-143.12

Why D is correct

For solder and flux, lead free means no more than 0.2 percent lead. The separate limit for pipes, pipe fittings, plumbing fittings and fixtures is a weighted average of 0.25 percent across wetted surfaces. These are different measurement bases, not a ranking of which number is stricter. Flux is expressly included in the solder-and-flux requirement. Neither treatment of the water nor small pipe diameter establishes either proposed exemption. Source: https://www.ecfr.gov/current/title-40/chapter-I/subchapter-D/part-143/subpart-B/section-143.12

2. What does the IPC require for a joint in hubless cast-iron soil pipe?

  • AA hot-poured lead and oakum joint packed at every connection and caulked tight so the joint holds against head pressure during the drainage test
  • A shielded coupling with an elastomeric sleeve and stainless steel clamps, tightened to the torque specified by the coupling manufacturer
  • CA solvent-cemented sleeve installed over the plain pipe ends, since the sleeve spans the gap and the cement seals it without any clamping
  • DA threaded coupling engaging not less than three full threads, which is the engagement accepted on threaded pipe joints

Where to look it up

https://www.charlottepipe.com/articles/cispi-310-a-guide-to-no-hub-cast-iron-connections

Why B is correct

Use the listed shielded sleeve coupling and tighten the clamps to the coupling manufacturer’s specified torque. Charlotte Pipe describes standard no-hub couplings as a gasket inside a stainless steel shield with clamps, and distinguishes medium- and heavy-duty couplings. Its standard coupling torque is 60 inch-pounds, but torque varies by product; do not apply that number to every coupling. Lead-and-oakum joints require a different hub-and-spigot arrangement, solvent cement does not join cast iron, and the plain no-hub ends are not threaded joints. Follow the applicable support requirements as well. Source: https://www.charlottepipe.com/articles/cispi-310-a-guide-to-no-hub-cast-iron-connections

3. The local frost line is 42 inches. The code requires water service pipe to be installed not less than 12 inches deep and not less than 6 inches below the frost line. What is the minimum depth of cover?

  • A42 inches of cover

    Forty-two inches places the pipe exactly at the frost line with no margin, ignoring the additional 6 inches the requirement adds below it. A pipe at the frost line freezes in a hard winter.

  • B12 inches of cover

    Twelve inches is the absolute minimum that applies where frost is not a factor. Applying it in a frost region ignores the requirement that actually governs here.

  • C54 inches of cover

    Fifty-four inches comes from adding the 12-inch absolute minimum to the frost line, treating two independent minimums as if they stack. They do not; the deeper of the two applies.

  • 48 inches of cover

Why D is correct

Where two minimum depths apply, the greater controls. The absolute floor is 12 inches of cover, and the frost requirement is the frost line plus 6 inches, which here is 42 plus 6 equals 48 inches. Forty-eight is greater than 12, so the service is buried with not less than 48 inches of cover. In a warm climate with no meaningful frost line, the 12-inch minimum would be the governing number instead.

What this question is testing

The item tests the ability to apply two simultaneous minimums correctly, taking the greater rather than adding them, and to work with a locally published value, the frost line, as given data. It is the same logic used whenever two code minimums bear on one dimension.

On the job

Frost depth is local and it is published by the jurisdiction, not calculated. Call the building department or check the local amendment before you price excavation, because in northern towns the difference between a 4-foot and a 6-foot trench changes the shoring, the spoil handling, and the machine you need. Also keep the service clear of the sewer trench and maintain the required horizontal separation between the two.

Memory technique

Frost line plus six, but never less than twelve; take the deeper number.

Exam tip

When two minimums apply to the same dimension, the deeper or larger one governs; never add them together.

Where to look it up

Chapter 3, protection of piping against freezing, plus the water service installation provisions in Chapter 6. Frost depth is set locally and the UPC states burial requirements differently, so confirm the depth with the authority having jurisdiction and the code your state adopted.

4. An underground water service outside a building is in noncontaminated soil. Under unamended 2021 IPC Section 605.3 and Table 605.3, which specified product meets the stated material, potable-water and minimum pressure-rating requirements?

  • AABS drainage-only pipe with no potable-water certification or service pressure rating
  • PEX water-service tubing conforming to ASTM F876 and NSF61, rated at least160 psi at73.4°F and for the highest available service pressure
  • CPVC pipe certified only for DWV use, with no pressure or potable-water rating
  • DCopper DWV tubing with no water-service pressure certification

Where to look it up

https://www.ncosfm.gov/b-1-2024-ncpc/open

Why B is correct

The PEX row includes ASTM F876. Section 605.3 requires NSF 61 compliance and at least 160 psi working-pressure rating at 73.4°F for underground outside service; where available pressure is higher, the product rating must cover it. Assess the actual product certifications, not just its plastic family or a DWV marking: pressure-rated ABS and PVC appear in the table, and dual-rated products cannot be rejected by name alone. See PDF pp.74-75. Source: 2021 IPC base text reproduced in NC OSFM comparison document, https://www.ncosfm.gov/b-1-2024-ncpc/open

5. PEX water tubing is being stored and installed where it will see direct sunlight for an extended period. What does the code require regarding that exposure?

  • APEX may be exposed to sunlight indefinitely, because the chlorine resistance rating printed on the tubing covers ultraviolet exposure as well
  • BPEX may be exposed to sunlight if it is coated with a latex primer that blocks ultraviolet light before the wall is closed
  • CSunlight has no effect on PEX, and only sustained temperatures above 180 degrees F will shorten the service life of the tubing in a hot water distribution line
  • PEX must be protected from ultraviolet exposure, and any exposure is limited to what the manufacturer's installation instructions and listing permit

Where to look it up

https://www.uponor.com/getmedia/3002f54f-d63c-4f3a-807f-70d91f620843/2023-2028-wi-listing-pp-022300004-ptoaafinalp?sitename=USA

Why D is correct

Protect PEX from ultraviolet exposure and follow the limits and installation conditions for the particular product. Chlorine resistance does not establish unlimited sunlight resistance. Do not assume a latex primer alone makes an exposed installation acceptable. Uponor permits certain latex and acrylic paints on AquaPEX as compatible materials, but paint compatibility is not evidence that the coating satisfies UV-exposure requirements. Check the current product instructions, listing and adopted requirements; exposure limits and conditions vary. Source: https://www.uponor.com/getmedia/3002f54f-d63c-4f3a-807f-70d91f620843/2023-2028-wi-listing-pp-022300004-ptoaafinalp?sitename=USA

6. Vertical copper water tubing is supported using the ordinary 2021 IPC Table 308.5 method, with no engineered-design exception. Where the floor-to-floor distance exceeds the table interval, what maximum spacing applies between vertical supports?

  • AAt each floor only, with no maximum interval
  • B4 feet
  • C15 feet
  • 10 feet

Where to look it up

https://www.ncosfm.gov/b-1-2024-ncpc/open

Why D is correct

Both copper-tubing size rows specify a maximum vertical spacing of 10 feet. Floor levels alone do not satisfy that interval when they are farther apart. Do not substitute the separate steel-pipe value or assume all materials have longer vertical intervals. The Section 308.5 engineered-design exception is excluded here. See PDF pp.32-33. Source: 2021 IPC base text reproduced in the NC OSFM comparison document, https://www.ncosfm.gov/b-1-2024-ncpc/open

7. A 3-inch waste line can drop only 9 inches between its upstream end and the stack because of a beam overhead. Take the required slope for that pipe size as 1/4 inch per foot, given. What is the longest developed length that the available fall will support?

  • A18 feet
  • 36 feet
  • C72 feet
  • D108 feet

Where to look it up

Explicit exercise assumptions; not a universal code requirement.

Why B is correct

Use the slope explicitly given in this question: maximum length = available fall / slope = 9 inches / (0.25 inch per foot) = 36 feet. Eighteen feet would use 0.5 inch per foot, 72 feet would use 0.125, and 108 feet would use about 0.0833; none uses the stated slope. This calculation does not establish the minimum slope in a particular adopted code or permit an exception to it. Confirm elevations and any additional drops separately when laying out the actual line.

8. A long copper hot-water main is subject to thermal expansion and contraction. Under 2021 IPC Section 305.2, what installation requirement addresses the resulting stress?

  • Provide suitable protection against damaging expansion/contraction so stresses do not exceed the pipe strength
  • BAdd rigid anchors until every movement is prevented, regardless of the resulting stress
  • CReduce operating pressure instead of evaluating thermal movement
  • DInsulate the pipe and omit any allowance for thermal movement

Where to look it up

https://www.ncosfm.gov/b-1-2024-ncpc/open

Why A is correct

Section 305.2 requires prevention of excessive pipe stress and, where necessary, protection from damage caused by expansion, contraction or structural settlement. The means must suit the installation; this is not a universal instruction to eliminate all movement or install an expansion joint everywhere. Insulation or pressure reduction does not replace that assessment. See PDF p.30. Source: 2021 IPC base text reproduced in the NC OSFM comparison document, https://www.ncosfm.gov/b-1-2024-ncpc/open

9. Approved, listed press-connect fittings suitable for the specified copper water-tube application are selected for an occupied-building repair where open flame is prohibited. Under the 2024 IPC material-installation requirements, how should the press joints be made?

  • Follow the applicable standards and manufacturer instructions, using manufacturer-approved compatible tools, jaws or rings and the specified tube preparation and insertion
  • BSolder every pressed connection afterward because a press joint is only temporary
  • CUse any pressing tool that physically fits, regardless of its compatibility approval
  • DOmit insertion checks because a listed fitting makes workmanship irrelevant

Where to look it up

https://shop.iccsafe.org/media/wysiwyg/material/3210S24-Sample.pdf

Why A is correct

IPC 303.2 requires installation under the applicable accepted standards and manufacturer instructions; 303.4 addresses third-party listing to referenced standards. The selected system still needs correct preparation and assembly. Manufacturer-approved compatibility does not necessarily mean the tool and fitting share a brand. Viega instructions, for example, require deburring, full insertion, an insertion mark and approved tooling. Do not assume every unpressed joint will reveal itself at every test pressure. Sources: 2024 IPC 303.2 and 303.4 (ICC public sample pp.3-4 and3-5), https://shop.iccsafe.org/media/wysiwyg/material/3210S24-Sample.pdf; Viega ES-PP0926, §§1.4(B),3.2 and3.4(G), https://www.viega.us/content/dam/viega-assets/viega-worldwide-assets/products/na-products/technical-documents/propress/engineering-specifications/ES-PP_ProPress_Fittings.pdf

10. Water distribution piping is to be hydrostatically tested. Take these criteria as given for this project: the test pressure must be at least 1.5 times the system's working pressure and in no case less than 100 pounds per square inch. The system's working pressure is 78 pounds per square inch. What is the minimum acceptable test pressure?

  • A78 pounds per square inch
  • B100 pounds per square inch
  • 117 pounds per square inch
  • D156 pounds per square inch

Where to look it up

Explicit exercise assumptions; not a universal code requirement.

Why C is correct

For this project, calculate 1.5 × 78 = 117 psi and compare it with the 100 psi floor. Both conditions must be met, so the minimum is 117 psi. A 78 psi or 100 psi test would fall short of the stated project requirement; 156 psi comes from an unspecified multiplier of 2. The calculation alone does not establish that 156 psi would damage equipment. Verify component ratings and the applicable test procedure, medium and duration before testing; the given project factors are not a universal plumbing-code rule.

45 more in the bank

Answers and explanations for these are in the app.

  • Among copper water tube types K, L, and M of the same nominal size, which type has the greatest wall thickness?
  • Which statement correctly describes where PVC and CPVC pipe are permitted in a potable water system under the IPC?
  • Under the IPC, where is PEX tubing permitted to be used?
  • What is the primary performance problem with galvanized steel water piping in older potable systems?
  • Copper tube is being tied into existing galvanized steel on a potable line. Which joining method does the IPC require at that transition?
  • How must joints in copper tubing used for fuel gas piping be made?
  • What surface preparation does the IPC require before solvent cementing a PVC drainage joint?
  • How does the IPC permit ABS drainage pipe to be connected to PVC drainage pipe?
  • How must a buried building sewer be bedded according to the IPC?
  • What is the IPC's basic requirement for supporting vertical piping?
  • A 4-inch building sewer is run at a uniform slope of 1/8 inch per foot, given. The developed length from the building to the point of connection is 96 feet. How much does the invert drop over that run?
  • You will fill 72 feet of 4-inch DWV piping for a water test. The pipe holds 0.65 gallon per foot, given. Approximately how many gallons will the fill require?
  • A DWV section is filled with water to a level 27 feet above the test tee at the base. Using 0.433 psi per foot of water column, given, what static pressure acts at the test tee?
  • Piping runs through a bored hole in a stud, and the hole is less than 1-1/4 inches from the face of the framing member. What does the IPC require?
  • Where are the limits on how much a load-bearing joist or stud may be notched or bored for plumbing piping found?
  • What does the IPC require where a pipe passes through a foundation wall?
  • After the sewer is laid and inspected, what backfill method does the IPC prescribe for closing the trench?
  • Drainage piping is being installed underground beneath a building. Under the IPC materials tables for drainage piping, which copper tubing is permitted for that underground portion?
  • PEX tubing must change direction sharply inside a framed wall. How may that change of direction be made?
  • A PEX water distribution system is being assembled and a substitute brand of fitting is proposed. Under the IPC, which fittings may be used to join that PEX tubing?
  • ABS drainage pipe is being assembled with solvent cement. Which statement correctly describes what that joint requires?
  • A connection is being made between an existing vitrified clay building sewer and new cast-iron pipe. How does the IPC require that connection to be made?
  • A flared joint is being made in copper water tubing. What does the IPC require for that joint to be acceptable?
  • A horizontal run of 3/4-inch copper water tubing is being hung. Under the piping support table, what is the maximum spacing permitted between hangers on that run?
  • A roof drain conductor will be installed inside a building and connected to an underground storm drain. What does the IPC require of the piping material used for that conductor?
  • A fitting is being selected for a horizontal drainage branch. What does the IPC require of fittings installed in drainage piping?
  • Previously used pipe, fittings and valves are being offered for installation in a new plumbing system. What does the code permit regarding the reuse of those materials?
  • An inspector questions a length of piping on which no manufacturer's markings are visible. What does the code require regarding identification of piping materials?
  • A 4-inch building drain must cover 96 feet of developed length between the stack base and the point of connection, and the elevations at the two ends leave 12 inches of fall available. Take the minimum slope for 4-inch drainage piping as 1/8 inch per foot, given. What slope does the available fall produce, and how does it compare with that minimum?
  • A water distribution riser in a tall building holds 40 psi at its highest point when no water is flowing. The lowest point of that riser is 210 feet below the highest point. Using 0.433 psi per foot of water column, what static pressure does the piping at the lowest point see?
  • A new water service consists of 240 feet of 1-1/2 inch pipe and 60 feet of 2-inch pipe. Take these capacities as given data: the 1-1/2 inch pipe holds 0.11 gallon per foot and the 2-inch pipe holds 0.17 gallon per foot. Approximately how many gallons of water does the completed service hold?
  • Piping is being installed so that it passes through a concrete slab. What does the IPC require at that penetration?
  • A threaded connection has to be made in a PVC water piping run so the pump can be removed for service. What does the plumbing code permit regarding threading plastic pipe?
  • An addition to an older building will extend existing galvanized steel water piping to a point outside the structure. How does the plumbing code treat galvanized steel pipe used underground?
  • Vent piping is being selected for a building whose drainage system is PVC. How does the plumbing code establish which materials may be used for the vents?
  • A cleanout is being installed on a cast-iron drainage line and the plug is being selected. What does the plumbing code require of that plug?
  • A 3-inch drain must offset 9 inches sideways to clear a duct, using a pair of 22-1/2 degree fittings. Take the 22-1/2 degree offset constant as 2.613, so that travel equals the offset multiplied by that constant. What is the travel between the two fittings?
  • A section of drainage piping to be water tested consists of a 3-inch stack standing 38 feet tall plus 55 feet of 4-inch horizontal piping, all of which will be filled. Take these capacities as given: 3-inch pipe holds 0.38 gallon per foot and 4-inch pipe holds 0.65 gallon per foot. Approximately how much water is needed to fill the section?
  • A new horizontal waste line has to be supported in a crowded ceiling space, and the easiest attachment points are the existing cast-iron drainage line and a nearby suspended ceiling grid. What does the plumbing code require of the supports?
  • A CPVC water line has been repaired with solvent-cemented joints and the building owner wants the water turned back on immediately. What governs when that piping may be pressurized and tested?
  • An underground water service will be run in copper tube. Which copper water tube is acceptable for that buried run?
  • A PVC water distribution line needs a 90-degree change of direction, and the only fitting left on the truck is a drainage pattern elbow of the same size and material. What does the plumbing code require?
  • CPVC piping is being installed on a continuously circulating hot water loop. What determines whether that material may be used in this application?
  • A horizontal drainage main must cross a structural expansion joint that divides a long building into two sections. What does the plumbing code require of the piping at that crossing?
  • An inspector asks how you can tell that a length of plastic pipe on the job is suitable for potable water. What should the markings on that pipe show?

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