22 Piping & Materials Practice Questions & Answers

1. 1. A technician has two 2-inch PVC pipes on the truck. One is printed 'Schedule 40' and the other 'Class 200.' As markings, what does each one describe?

   • A.Schedule names a pressure rating in psi; class states the pipe's wall-thickness series
   • B.Both name a pressure rating, but schedule is rated at a colder water temperature
   • C.Schedule names a wall-thickness series; class states the pipe's pressure rating in psi✓ Answer
   • D.Both name a wall-thickness series, but class is measured from the inside diameter

   Schedule is a dimensional series: the wall thickness follows a set schedule for each nominal size, so the pressure a pipe will hold is a consequence of those dimensions and it changes with diameter. Class is stated as the pressure rating itself, and it is held constant across sizes by holding the diameter-to-wall ratio constant.

   Source: ASTM D1785 (PVC Schedule 40/80) and ASTM D2241 (PVC pressure-rated pipe, SDR series)Report a problem with this question

2. 2. A supplier's chart lists Schedule 40 PVC at 450 psi in 1-inch, 220 psi in 4-inch and 180 psi in 6-inch, while Class 200 PVC is listed at 200 psi in every size shown. Which statement explains that pattern?

   • A.Class pipe follows a set wall thickness for each size, so its rating holds steady across sizes
   • B.Schedule pipe follows a set wall thickness for each size, so its rating rises as diameter grows
   • C.Class pipe follows a set outside diameter for each size, so its rating holds steady across sizes
   • D.Schedule pipe follows a set wall thickness for each size, so its rating falls as diameter grows✓ Answer

   In the schedule series the wall thickness is set by the schedule rather than by the pressure wanted, so as the nominal size grows the wall becomes thinner in proportion to the diameter and the pressure rating drops. Class pipe holds a constant ratio of outside diameter to wall thickness, which is why every size in a class carries the same rating.

   Source: ASTM D1785 (PVC Schedule 40/80) and ASTM D2241 (PVC pressure-rated pipe, SDR series)Report a problem with this question

3. 3. PVC pressure pipe is rated by PR = 2S / (SDR - 1), where S is the hydrostatic design stress; take S as 2,000 psi for PVC 1120 at 73°F. A length of pipe is printed 'SDR 26.' What pressure rating does the formula give at that temperature?

   • A.200 psi
   • B.250 psi
   • C.125 psi
   • D.160 psi✓ Answer

   Substituting gives PR = (2 x 2,000) / (26 - 1) = 4,000 / 25 = 160 psi, which is why pipe of this ratio is sold as Class 160. Because the ratio is held constant, the same arithmetic returns 160 psi in every nominal size of that class.

   Source: ASTM D2241, PVC pressure-rated pipe (SDR series)Report a problem with this question

4. 4. Two 2-inch PVC pipes are marked SDR 13.5 and SDR 26. SDR is the pipe's outside diameter divided by its minimum wall thickness. Which pipe has the thicker wall and the higher pressure rating, and why?

   • A.SDR 13.5, because the number is a direct count of the pipe's working pressure in hundreds
   • B.SDR 13.5, because a smaller ratio means the wall is thicker in proportion to the diameter✓ Answer
   • C.SDR 26, because the ratio compares the wall against the inside rather than the outside diameter
   • D.SDR 26, because a larger ratio means more wall material in proportion to the diameter

   SDR is outside diameter divided by wall thickness, so a low number means the wall is a large fraction of the diameter. Since the pressure a pipe holds rises with wall thickness relative to diameter, the lower SDR is always the stronger, higher-rated pipe.

   Source: ASTM D2241, PVC pressure-rated pipe (SDR series)Report a problem with this question

5. 5. A 1 1/2-inch lateral is being replaced and the crew may use either Schedule 40 or Class 200 PVC in the same nominal size. How do the two compare for flow?

   • A.Class 200 has the thinner wall, so a larger inside diameter and less friction loss at a given flow✓ Answer
   • B.Class 200 has the thicker wall, so a smaller inside diameter and more friction loss at a given flow
   • C.Both pipes share one inside diameter, so friction loss at a given flow is the same in either one
   • D.Schedule 40 has the thinner wall, so a larger inside diameter and less friction loss at a given flow

   Plastic pipe of a given nominal size shares one outside diameter, so any extra wall thickness is taken out of the bore. Schedule 40 is the thicker of the two here, which leaves it a smaller inside diameter, a higher velocity at the same flow, and more friction loss than Class 200.

   Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - pipe sizing and friction lossReport a problem with this question

6. 6. A technician works in a northern climate where laterals cannot always be drained completely and shallow lines may freeze. Which piping choice best fits that condition, and why?

   • A.Polyethylene, because it stays flexible when cold and yields as ice expands inside the line✓ Answer
   • B.Copper tubing, because its high conductivity keeps the water inside it above freezing longer
   • C.Galvanized steel, because threaded metal joints hold when the pipe is loaded by ice
   • D.Schedule 80 PVC, because a thicker rigid wall stops ice from expanding inside the line

   Polyethylene is ductile and stays flexible at low temperature, so it stretches and recovers when trapped water freezes and expands. PVC becomes more brittle and more notch-sensitive as temperature falls, and no rigid pipe can contain the expansion of ice no matter how thick its wall.

   Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - pipe material selectionReport a problem with this question

7. 7. A technician primes the socket of a 2-inch fitting, is called away, and returns ten minutes later to find the primed surface dry to the touch. What should be done before cementing?

   • A.Scuff the socket with emery cloth and cement it, since primer is only a code marker
   • B.Re-apply primer so the surface is soft and still wet when the cement is spread on it✓ Answer
   • C.Wipe the socket with a dry rag and cement it, since primer only cleans the surface
   • D.Apply an extra-heavy coat of cement, which will re-soften the dried primer as it sets

   The primer's job is to soften and dissolve the pipe and socket surfaces so the cement can penetrate them and the two parts fuse into one piece. Once the primed film has dried, that softened layer is gone, so primer must be re-applied and the cement put on while it is still wet and fluid.

   Source: ASTM D2855, two-step solvent cementing of PVC pipe and fittingsReport a problem with this question

8. 8. During a dry fit, a 1-inch pipe end slides freely all the way to the bottom of the fitting socket with no resistance at any point. What does that tell the technician?

   • A.The pipe was cut too short, so the cement will have to bridge a gap in the socket
   • B.The fit is correct, because a clean tapered socket takes the pipe in without resistance
   • C.The fit is out of tolerance, because a tapered socket should grip the pipe before it bottoms✓ Answer
   • D.The socket is dirty, so a solvent wipe will restore the grip the connection needs

   Solvent-weld sockets are tapered on purpose so that the pipe meets an interference fit part-way in and is held there while the cement works. A pipe that drops freely to the bottom dry means pipe or fitting is out of tolerance, and the joint will be starved of contact and prone to leak.

   Source: ASTM D2855, two-step solvent cementing of PVC pipe and fittingsReport a problem with this question

9. 9. Joints on a mainline were solvent welded at 55°F in damp, humid weather. Two hours later the crew wants to pressure-test the line. What governs that decision?

   • A.Cure time governs the test, and cool damp conditions extend it beyond the dry-weather figure✓ Answer
   • B.Cure time governs the test, but humidity and temperature do not change the label figure
   • C.Set time governs the test, and once a joint can be handled the line may be pressurized
   • D.Set time governs the test, and cool weather shortens it because the cement stiffens fast

   Set time only means the joint may be handled; cure time is when it has developed the strength to take pressure. Solvent leaves the joint more slowly in cool, humid air, so cure time must be extended - commonly about half again as long - and the cement manufacturer's published schedule is the governing figure.

   Source: ASTM D2855 and solvent cement manufacturers' published set and cure schedulesReport a problem with this question

10. 10. A leaking joint is cut out and split open. Much of the socket wall is bare glossy PVC, cement shows only in streaks, and no bead had formed around the outside of the joint. What most likely happened?

    • A.The pipe went in before the primer flashed, and the wet primer thinned the cement
    • B.Too much cement was applied and the surplus was pushed clear of the whole socket wall
    • C.Too little cement was applied and it skinned over before insertion, so nothing fused✓ Answer
    • D.The joint was held too long, and holding squeezed the cement film out of the socket

    A dry or cold joint is one where there was not enough cement, or the cement had begun to set before the pipe went in, so the two surfaces never softened and fused into a single mass and the joint holds only by friction. A properly made joint shows a continuous bead of cement all the way around the socket mouth.

    Source: ASTM D2855, two-step solvent cementing of PVC pipe and fittingsReport a problem with this question

11. 11. A PVC female threaded ell split along its length the day after a brass male nipple was made up hand tight plus roughly four wrench turns. What is the mechanism of that failure?

    • A.The tapered male thread acted as a wedge and stretched the plastic socket until it split✓ Answer
    • B.The nipple seated on the fitting shoulder, which is the surface an NPT thread seals on
    • C.The pipe sealant softened the plastic chemically and the socket lost its hoop strength
    • D.The brass and the plastic cooled overnight at different rates and pulled the socket apart

    NPT threads are tapered, so every extra turn drives the male thread deeper and forces the female fitting outward in hoop tension, and plastic has little reserve for that. Hand tight plus one to two turns with a wrench is the limit; thread sealant lubricates the threads and makes it even easier to go past it.

    Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - threaded connectionsReport a problem with this question

12. 12. A transition at a riser can be made with a plastic male adapter into a metal female fitting, or with a metal male nipple into a plastic female fitting. Which arrangement is preferred, and why?

    • A.Male metal into female plastic, because a plastic female flexes and will never crack
    • B.Male plastic into female metal, because the metal female resists the hoop stress of wedging✓ Answer
    • C.Male plastic into female plastic, because matched materials expand at the same rate
    • D.Male metal into female plastic, because metal threads cut a tighter seal in the plastic

    The tapered male thread always tries to spread the female fitting apart, so the part that must resist hoop tension should be the metal one. Putting a metal male into a plastic female is the highest-risk combination and is where split fittings normally come from.

    Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - threaded connectionsReport a problem with this question

13. 13. A technician is making up a male-threaded PVC adapter into a female brass ell. Which practice correctly seals that joint?

    • A.Wrap two to three turns of PTFE tape on the male threads, against the tightening direction
    • B.Wrap two to three turns of PTFE tape on the male threads, in the tightening direction✓ Answer
    • C.Wrap two to three turns of PTFE tape on the female threads, in the tightening direction
    • D.Brush solvent cement over the male threads, since it is compatible with the PVC adapter

    Sealant belongs on the male thread only, and PTFE tape is wound in the direction the fitting turns as it is tightened so that make-up presses the tape into the thread instead of unwinding it off the end. Solvent cement is not a thread sealant: it cannot seal a taper thread and it must never be brushed on threads.

    Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - thread sealants and threaded jointsReport a problem with this question

14. 14. A large-diameter gasketed bell-and-spigot PVC mainline is being assembled in the trench. Which practice is correct for these joints?

    • A.Lubricate with soapy water and skip thrust blocks, since gaskets restrain the thrust
    • B.Lubricate with a petroleum grease and drive the spigot hard against the bell bottom
    • C.Lubricate with solvent primer and then cement the gasket in place inside the bell
    • D.Lubricate with the gasket lubricant supplied and stop at the spigot's insertion mark✓ Answer

    Gasketed joints are made with the manufacturer's approved non-petroleum lubricant, and the spigot is pushed only to its reference mark so the joint keeps room to take up thermal movement. The joint is not restrained, so direction changes, tees and dead ends still need thrust blocking against undisturbed soil.

    Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - gasketed pipe joints and thrust blockingReport a problem with this question

15. 15. A 2-inch pipe is cut slightly out of square with a handsaw, and the outside edge is not chamfered before cementing. What is the most likely result?

    • A.The end will fall short of the socket depth and pull free the first time the line surges
    • B.The end will not seat evenly and it scrapes cement out of the socket as it is pushed in✓ Answer
    • C.The end will bottom too deeply and the pipe will restrict flow inside the fitting body
    • D.The end will cure unevenly and the temperature difference will crack the socket wall

    A square, chamfered end enters the tapered socket cleanly and lets the cement stay where it was applied. A blunt, angled end acts like a scraper, plowing the cement ahead of it and leaving an unfused path straight through the joint; the chamfer is cut at roughly 10 to 15 degrees around the outside edge.

    Source: ASTM D2855, pipe end preparation for solvent cementingReport a problem with this question

16. 16. On a cold morning a ratchet-type cutter leaves the ends of 1 1/2-inch PVC slightly oval with a raised burr on the inside. What is the correct response?

    • A.Ream the burr away and switch to a wheel cutter or a fine-tooth saw for this size✓ Answer
    • B.Dress the end with a handheld disc grinder to true the oval before cement is applied
    • C.Heat the end with a torch until the oval relaxes, then cement the joint as it was cut
    • D.Leave the burr in place, because moving water will wear it smooth within a few cycles

    An inside burr obstructs flow and catches debris, and an ovalled end cannot bottom uniformly in a round socket, so the burr is reamed and a tool that leaves a clean square end is used instead. Ratchet cutters deform pipe most in cold weather and on larger sizes, and handheld disc grinders are not an accepted way to dress or chamfer PVC.

    Source: ASTM D2855 and Irrigation Association guidance on tool selection for cutting PVC pipeReport a problem with this question

17. 17. A polyethylene lateral is being joined to a barbed insert fitting on a run that stays pressurized. Which assembly is correct?

    • A.Push the barb fully home and set two stainless clamps over the barbs, opposed 180°✓ Answer
    • B.Push the barb fully home and leave it unclamped, since clamps crush poly over time
    • C.Push the barb in halfway and cement the remaining gap so the joint cannot pull apart
    • D.Push the barb fully home and set one clamp behind the barbs on the plain tubing wall

    Polyethylene is joined mechanically, not chemically: the barb is seated to its shoulder and the clamps go over the barbs, where the tubing is stretched onto the ridges and the seal is actually made. Two clamps set 180° apart are standard on pressurized and larger connections, and solvent cement does not bond polyethylene at all.

    Source: ASTM D2609, plastic insert fittings for polyethylene pipeReport a problem with this question

18. 18. Polyethylene pipe for insert fittings is sized by SIDR, the average inside diameter divided by the minimum wall thickness. A crew has SIDR 9 and SIDR 15 poly in the same nominal size. Which statement is correct?

    • A.SIDR 15 has the larger inside diameter, so it needs a thicker barb on the insert fitting
    • B.SIDR 9 has the smaller inside diameter, so it needs a thinner barb on the insert fitting
    • C.SIDR 9 has the thicker wall and the higher rating, and both take the same insert fitting✓ Answer
    • D.SIDR 15 has the thicker wall and the higher rating, and both take the same insert fitting

    SIDR is measured from the inside diameter, so the bore stays the same for a nominal size no matter the pressure class and one barb size fits them all - the extra wall is added outward. As with SDR, a lower number means a thicker wall in proportion to the bore and therefore a higher pressure rating.

    Source: ASTM D2239, polyethylene plastic pipe (SIDR-PR), with ASTM D2609 insert fittingsReport a problem with this question

19. 19. At a point of connection a copper service line is joined directly to a galvanized steel nipple, and after two seasons the junction is heavily corroded and scaling. What explains it, and what is the fix?

    • A.Erosion from high velocity at the change in bore; a larger nipple slows the water down
    • B.Galvanic action between dissimilar metals; more PTFE tape seals the threads against it
    • C.Thermal cycling at the rigid junction; a flexible connector absorbs the daily movement
    • D.Galvanic action between dissimilar metals; a dielectric union separates them electrically✓ Answer

    Copper and galvanized steel sit far apart electrically, so when they touch in the presence of water a current flows and the more active metal corrodes away at the joint. A dielectric union is the correct transition fitting because it interrupts the metallic path between them; tape seals a thread but leaves the two metals in electrical contact.

    Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - dissimilar-material transitionsReport a problem with this question

20. 20. A long PVC lateral is solvent welded beside the trench on a hot afternoon, then pulled straight and tight in the trench before backfill. Why should it be laid in a gentle S instead?

    • A.Contraction as the pipe cools raises internal pressure unless slack is left in the run
    • B.Contraction as the pipe cools puts the joints in tension unless slack is left in the run✓ Answer
    • C.Snaking spreads thrust at bends across a wider face of undisturbed soil in the trench
    • D.Snaking lets each head be brought up to finished grade after the trench is backfilled

    PVC welded hot is at its longest, and it shortens as it cools and again as ground temperature drops in winter; a run pulled taut has nowhere to give, so that movement is carried straight into the joints. Snaking stores the slack. Thrust at bends is carried by thrust blocking, and setting a head to grade is what a swing joint does.

    Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - pipe installation and thermal movementReport a problem with this question

21. 21. A buried lateral fails in its first season. Excavated, it shows a long split running lengthwise where a fist-sized rock in the backfill bore against the top of the pipe. Which practice would have prevented it?

    • A.Backfill in a single lift and water-settle it, since compactors crack PVC pipe
    • B.Bed and backfill the first layer with rock-free material, compacted alongside the pipe✓ Answer
    • C.Backfill the trench with the coarsest spoil on hand so that water drains away above it
    • D.Bed the pipe on a row of bricks so the backfill load bridges over the run instead

    PVC is notch-sensitive, so a point load from a rock concentrates stress in one spot of the wall and starts a crack that then runs lengthwise under pressure cycling. Rock-free bedding and a compacted first layer of select material spread the load evenly along the barrel instead of into one point.

    Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - trenching, bedding and backfillReport a problem with this question

22. 22. A zone runs at low pressure and a wet, sunken strip appears above one lateral. After locating and exposing the break, what sequence should the technician follow?

    • A.Shut the water off, cut the damaged section out, dry the ends, then fit a repair coupling✓ Answer
    • B.Leave the water on to flush the line, then cement a repair coupling over the wet break
    • C.Shut the water off, then cement a sleeve over the split without cutting the pipe apart
    • D.Shut the water off, cut the break out, and backfill at once so the trench does not cave

    Solvent cement will not weld a wet or dirty surface and it cannot bond across an existing crack, so the damaged length has to come out and clean, dry, square ends must be prepared for a slip or repair coupling. The new joints are then left to cure before the line is pressurized and the trench is closed.

    Source: Irrigation Association, Landscape Irrigation System Installation and Maintenance - locating and repairing pipe breaksReport a problem with this question

Practice questions based on the Irrigation Association's published Certified Irrigation Technician content — basic irrigation principles, basic electrical principles and basic hydraulics — together with standard irrigation installation, hydraulics and backflow-prevention references. This site is not affiliated with or endorsed by the Irrigation Association. Irrigation work is governed by local plumbing and irrigation codes, water-purveyor rules and licensing that vary by jurisdiction; backflow assemblies in particular must be selected, installed and tested to the rules in force where you work. Confirm current exam requirements with the Irrigation Association before testing. About IA certification →