306A cutting, bending and joining pipe practice questions.

Five free practice questions on cutting, bending and joining pipe: block B of the Red Seal 306A Plumber exam, about 13 of its 125 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.

01The questions

1. Procedural · Joins plastic tube, tubing and pipe

   You are laying 6-inch (150 mm) SDR 35 PVC gasketed sewer pipe from a new car wash to the property line. The spigot is chamfered and the gasket is seated in the bell. How is the joint made?

   1. Apply PVC cement in the bell over the gasket for a double seal
   2. Lubricate with the maker's gasket lubricant; push to the depth mark
   3. Drive the spigot until it bottoms out hard in the bell
   4. Coat the gasket with pipe dope so it slides and seals
   Show the answer

   B. Correct. The maker's lubricant on spigot and gasket lets the spigot slide without rolling the gasket, and pushing to the insertion mark (not to the bottom of the bell) leaves room for movement. Lay the pipe with the bells upstream and check the gasket is still seated.

   Why not the others

   A. A gasketed joint is a compression seal; cement cannot bond across the gasket and stops the joint moving as designed. Lubricate with the maker's lubricant and push to the mark.

   C. Bottoming the spigot removes the joint's room for thermal movement and settlement, and hard driving can push the gasket out of its groove. Push only to the maker's insertion mark.

   D. Pipe dope and petroleum greases can swell or soften the rubber gasket and are not made for this. Use the maker's gasket lubricant and push the spigot to the insertion mark.

2. Procedural · Bends tube, tubing and pipe

   You are routing 3/4-inch (19 mm) PEX-A tubing (7/8-in OD) at a seniors' residence. The maker gives a minimum bend radius of 6 × the tube OD without a bend support. What is the tightest radius you may bend it to?

   1. 7 in
   2. 5 1/4 in
   3. 3 1/2 in
   4. 4 1/2 in
   Show the answer

   B. Correct. Minimum radius = 6 × OD = 6 × 7/8 = 5 1/4 in (about 133 mm). PEX is sized like copper tube, so 3/4-inch PEX is 7/8 in OD. Bending tighter risks a kink; where the run needs a tighter turn, use a bend support or an elbow fitting.

   Why not the others

   A. This uses 8 × OD (8 × 7/8), which is more conservative than the maker asks for. The stated minimum is 6 × OD = 5 1/4 in.

   C. This uses 4 × OD (4 × 7/8). The maker's factor for this tubing without a support is 6: 6 × 7/8 = 5 1/4 in. Tighter bends need a bend support or a fitting.

   D. This multiplies the nominal size, 3/4 in, by 6. The factor applies to the actual OD, 7/8 in: 6 × 7/8 = 5 1/4 in.

3. Recall · Joins cast iron pipe

   In a traditional caulked hub-and-spigot joint on old cast-iron drainage, what is the job of the oakum?

   1. It is packed tight and swells to form the seal
   2. It lubricates the spigot so it can be driven home
   3. It is filler only; the lead alone makes the seal
   4. It insulates the pipe so the lead cools slowly
   Show the answer

   A. Correct. Oakum (tarred hemp) is packed into the hub around the spigot and swells when wet to seal the joint; molten lead or a cold caulking compound on top locks it in place. When opening these joints in service work, treat the old lead as a hazard.

   Why not the others

   B. Lubricant is for compression-gasket joints. In a caulked joint the spigot is already in the hub and the oakum is packed around it, where it swells to make the seal.

   C. The lead, or cold caulking compound, holds the oakum in place; the oakum, packed tight and swollen with water, is what seals. The two work together.

   D. Slow cooling is not the aim. Oakum's job is to seal, packed tight and swollen with water, while the lead or cold caulking compound on top retains it.

4. Recall · Prepares tube, tubing and pipe connections

   Which grooving method is used to prepare thin-wall Schedule 10 steel pipe for grooved couplings?

   1. Roll grooving, which displaces metal instead of removing it
   2. Cut grooving, which machines the groove into the wall
   3. Threading, then a threaded coupling
   4. Cut grooving to half the normal depth
   Show the answer

   A. Correct. A roll groover presses the groove into the wall without removing metal, so it suits light-wall pipe such as Schedule 10 and is widely used on Schedule 40 too. Cut grooving removes metal and needs standard wall or heavier.

   Why not the others

   B. Cut grooving removes metal to the groove depth, which would leave too little wall on Schedule 10. It is used on standard-wall and heavier pipe. Thin wall is roll-grooved.

   C. Threading is not a grooving method, and a thread cut into Schedule 10 would take most of the wall. Light-wall pipe for grooved couplings is roll-grooved.

   D. A groove shallower than the maker's chart will not hold the coupling key, so the joint can pull apart. Light-wall pipe is roll-grooved to full chart depth, which displaces metal rather than removing it.

5. Procedural · Joins specialized tube, tubing and pipe

   A section of old asbestos-cement water service in a rural subdivision must be cut out to fit a repair coupling. The work falls under the provincial asbestos regulation for this material. How is the cut made?

   1. Keep it wet, cut with a manual snap cutter, bag the waste
   2. Saw it and clean up the dust with a shop vacuum
   3. Break the section out with a sledgehammer to avoid cutting
   4. Cut it dry with an abrasive saw, wearing a dust mask
   Show the answer

   A. Correct. Asbestos-cement pipe is cut with non-powered tools, such as a snap cutter, and kept wet so fibres stay bound. Wear the respirator the regulation requires and bag and label the offcuts and debris as asbestos waste for approved disposal.

   Why not the others

   B. A shop vacuum blows fine asbestos fibres back into the air; only a HEPA unit is acceptable for clean-up, and power sawing creates the dust in the first place. Wet the pipe, snap-cut it by hand, and bag the waste.

   C. Smashing asbestos-cement releases fibres and leaves ragged ends a coupling cannot seal on. Wet the pipe and cut it with a manual snap cutter.

   D. A dry abrasive saw turns the pipe into airborne asbestos dust, and a dust mask does not stop fibres. Keep the pipe wet, cut it with a manual snap cutter, and bag the waste.

02Answer key

03What block B covers

This block covers getting pipe ready and putting it together. It includes inspecting pipe and fittings for cracks and certification marks, cutting, reaming and bending copper, PEX and steel, threading, roll grooving and weld bevels, soldering and brazing copper, solvent welding PVC and ABS, PEX expansion joints, HDPE butt fusion, press and push-fit fittings, flanges, grooved couplings, hubless cast iron and transition couplings.

The Red Seal Occupational Standard names this block “Prepares and assembles tube, tubing and pipe”. It carries 10.4% of the exam, about 13 of the 125 questions, split across two tasks. The share column is each task's weight within the block, as the standard publishes it.

04What the questions turn on

Copper is sized by outside diameter

Copper water and DWV tube has an outside diameter 1/8 in larger than its nominal size, so 3/4 in tube is 7/8 in OD. Types K, L and M share that OD. Benders, cutters and PEX bend radii all work from the OD.

Heat the fitting, feed opposite

Heat the fitting socket and feed solder at the joint opposite the flame, so capillary action draws it through toward the heat. Black, burnt flux with solder sitting as a ring at the socket face means the joint was overheated.

Cure time before the test

A solvent weld gains strength as the solvent evaporates, and cold slows that a great deal. The cement maker's chart lengthens cure time as temperature drops and as pipe size and test pressure rise. PEX is never solvent welded; its joints are mechanical.

Thrust on hubless cast iron

Test water pushes at every change of direction: 10 ft of head is 4.33 psi, about 122 lb on a 6 in 90° bend. Horizontal hubless pipe and fittings 5 in and larger are restrained at every change of direction and branch.

05The other blocks

The 306A exam has seven blocks. Each has its own page of free questions:

The 306A Plumber practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.