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newSchoolWorks.com › VoTechWorks › Building & Construction › Plumbing & Pipefitting › Water Supply Systems: Design, Installation, and Testing › Lesson 3
BLD-PLUM06-04 · Lesson 3 · 15 clock hours · lab

Joining Methods: Soldering, Press, Push-Fit, PEX Expansion, and Crimp

Objective. Students will produce a leak-free joint in copper (solder), copper (press fitting), CPVC (solvent cement), PEX-A (expansion), and PEX-B (crimp) that passes a visual inspection and a 100 psi air test.

Why Joining Method Choice Matters

Every water supply system is only as reliable as its weakest joint. Plumbers work with copper, CPVC, and cross-linked polyethylene (PEX) daily, and each material demands a specific joining technique. Choosing the wrong method — or executing the right method poorly — produces leaks that can cause structural damage, mold, and costly callbacks. This lab teaches you to make five types of leak-free joints and verify each one at 100 psi.

Safety First

Before any tool touches any pipe, establish your safety baseline.

Method 1: Sweat Soldering (Copper)

Sweat soldering uses capillary action to draw molten solder into the gap between a copper fitting and tube.

1. Cut and deburr: Cut the tube square and remove the burr inside and outside with a deburring tool.

2. Clean: Abrade the outside of the tube end and the inside of the fitting socket with emery cloth or a fitting brush until the metal is bright and shiny.

3. Flux: Apply lead-free flux to both mating surfaces with a flux brush. Flux removes residual oxides and helps solder flow.

4. Assemble: Push the tube fully into the fitting socket and give it a quarter turn to spread flux evenly.

5. Heat: Apply torch heat to the fitting body — not the solder — moving the flame in small circles. Touch solder to the joint (not the flame) periodically. When the fitting is hot enough, solder feeds in by capillary action. Stop feeding when solder appears around the full circumference of the socket.

6. Cool: Allow the joint to cool undisturbed. Wipe with a damp rag to remove flux residue before the flux etches the copper.

Method 2: Press Fitting (Copper)

Press fittings use a press tool to mechanically compress an O-ring against the tube, creating a watertight seal without heat.

1. Cut and deburr the tube as for soldering.

2. Mark the insertion depth on the tube. Push the tube fully into the press fitting until the mark disappears inside the socket.

3. Place the correct jaw size for the fitting on the press tool, position it over the fitting collar, and squeeze the tool to full cycle. A complete press is indicated by the tool's indicator or an audible click depending on the tool model.

4. Inspect: the collar should be uniformly deformed with no gaps.

Method 3: Solvent Cement (CPVC)

Solvent cement chemically fuses CPVC pipe and fittings — it is not glue; it dissolves the surface and creates a molecular bond.

1. Cut CPVC square and deburr. Dry-fit to confirm full insertion depth.

2. Apply CPVC primer (if required by your local code or fitting manufacturer) to both surfaces, let flash off.

3. Apply a uniform coat of CPVC solvent cement to the pipe OD and fitting socket. Work quickly — open time is short, typically measured in seconds in warm conditions.

4. Push the pipe into the socket with a slight twisting motion and hold for the time specified on the cement can (commonly 30 seconds).

5. Wipe excess cement. Do not disturb the joint during the cure time listed on the can. Do not pressure-test until full cure is achieved.

Method 4: PEX-A Expansion (Uponor/Wirsbo Style)

PEX-A expansion uses an expansion tool to enlarge the pipe end and a separate expansion ring. The pipe's plastic memory shrinks it back down over the fitting barb.

1. Slide the correct-size expansion ring (PEX ring) onto the pipe before expanding.

2. Insert the expansion tool mandrel into the pipe end and squeeze the handles to expand the pipe and ring together. Rotate slightly and repeat several times around the circumference for a uniform flare.

3. Immediately push the fitting barb fully into the expanded pipe end. The ring must sit flush to the fitting shoulder.

4. The pipe contracts over the barb as it returns to its original diameter. In cold conditions allow more time for contraction before testing.

Method 5: PEX-B Crimp (Copper or Stainless Ring)

PEX-B crimp uses a copper or stainless crimp ring compressed by a crimp tool.

1. Slide the crimp ring onto the pipe end, leaving the ring back slightly from the pipe end.

2. Push the fitting barb fully into the pipe. Slide the crimp ring to between ⅛" and ¼" from the pipe end, centered over the barb's first ridge.

3. Position the crimp tool jaws perpendicular to the ring and squeeze to full closure.

4. Check with a go/no-go gauge. The go side must pass over the ring; the no-go side must not. A ring that fails the gauge must be cut off and remade.

Pressure Verification

After all joints are made, cap the assembly, connect a hand air pump, charge to 100 psi, and observe the pressure gauge for 5 minutes. No pressure drop is acceptable. If a joint fails, record the joint number, method, and probable defect in the defect log, disassemble, and remake the joint.

Key terms8

Capillary actionThe tendency of liquid solder to flow into a tight fitting-to-tube gap when drawn by surface tension and heat, making sweat soldering possible.
Lead-free solderSolder formulated to contain no more than 0.2% lead, required by federal law for joints in potable water systems.
Solvent cementA chemical compound that dissolves and fuses the surfaces of thermoplastic pipe and fittings (such as CPVC) to form a molecular bond rather than an adhesive joint.
PEX-A expansionA PEX joining method in which an expansion tool enlarges the pipe end and ring; the pipe's plastic memory then contracts it tightly over the fitting barb.
Crimp ringA copper or stainless steel ring that is mechanically compressed over a PEX pipe-and-barb fitting connection using a crimp tool.
Go/no-go gaugeA two-sided inspection tool used to verify a PEX crimp ring has been compressed to the correct diameter: the go side must slide over the ring; the no-go side must not.
Press fittingA mechanical fitting that creates a watertight seal by compressing an internal O-ring against the copper tube wall using a powered press tool, eliminating the need for heat.
FluxA chemical paste applied to copper surfaces before soldering that removes oxides and promotes solder flow; must be lead-free for potable water work and wiped off after the joint cools.

Worked examples3

1. You charge a 5-joint copper solder assembly to 100 psi. After 5 minutes the gauge reads 94 psi. How many psi of pressure loss occurred, and does the assembly pass?
  1. Record starting pressure: 100 psi.
  2. Record ending pressure: 94 psi.
  3. Calculate loss: 100 − 94 = 6 psi drop.
  4. Compare to acceptance criterion: zero pressure drop required over 5 minutes.
  5. 6 psi > 0 psi, so the assembly fails.
Answer: The assembly lost 6 psi and does not pass. All joints must be inspected, the leaking joint identified and logged, then remade and re-tested.
2. A crimp ring measures 0.651 inches after compression. The go gauge maximum is 0.652 inches and the no-go gauge minimum is 0.640 inches. Does the ring pass?
  1. Go-gauge check: the go gauge (max 0.652") must slide over the ring. The ring is 0.651", which is less than 0.652", so the go gauge slides over. Go check: PASS.
  2. No-go gauge check: the no-go gauge (min 0.640") must not slide over the ring. The ring is 0.651", which is larger than 0.640", so the no-go gauge is stopped. No-go check: PASS.
  3. Both checks pass, so the crimp ring is within the acceptable size range.
Answer: The crimp ring passes both the go and no-go gauge checks and is acceptable.
3. You need to make 2 joints per method for 5 methods. Your technique rubric score must be at least 80% on at least 8 of 10 joints. If you score below 80% on 3 joints, do you meet the requirement?
  1. Total joints: 2 methods × 5 joints per method = 10 joints. Wait — restate: 5 methods × 2 joints each = 10 joints total.
  2. Requirement: at least 8 of 10 joints must score ≥ 80%.
  3. If 3 joints score below 80%, then joints scoring ≥ 80% = 10 − 3 = 7 joints.
  4. Compare: 7 < 8. The requirement is not met.
Answer: No. Scoring below 80% on 3 joints leaves only 7 joints at or above 80%, which is one short of the required 8. At least 2 of the 3 low-scoring joints must be improved.
In class: Instructor-led demonstration of each joining method in sequence, emphasizing surface preparation (cleaning, fluxing, drying), heat application direction for solder, solvent cement open time for CPVC, correct ring placement for PEX expansion and crimp; students take notes and ask clarifying questions before attempting each method. · Hands-on joint production: each student makes two joints per method (10 joints total) on prepared spool pieces; instructor circulates and scores technique using a rubric that checks cleaning, flux coverage, heat angle, full insertion, and ring seating. · Pressure verification: student-made assemblies are capped, charged to 100 psi with a hand pump, and observed for 5 minutes; any joint that drops pressure is disassembled, defect identified on a defect log sheet, and re-made until leak-free.
Materials: Copper tube Type L (1/2" and 3/4"), CPVC pipe and fittings, PEX-A and PEX-B with appropriate fittings, lead-free solder, lead-free flux, flux brush, propane/MAPP torches, fire-resistant backing board, press tool with jaws, PEX expansion tool, PEX crimp tool, go/no-go gauge, push-fit fittings, hand air pump, pressure gauge, safety glasses, leather gloves, fire extinguisher, IPC
Check: All 10 joints pass 100 psi air test with zero pressure drop over 5 minutes; defect log fully completed for any failed joints; rubric score of at least 80% on technique for at least 8 of 10 joints

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

NCCER Plumbing L2 – Copper Pipe and Fittings
1. When sweat soldering copper, where should torch heat primarily be applied?
NCCER Plumbing L1 – Plumbing Safety and Materials
2. What federal requirement applies to solder and flux used on potable water piping?
NCCER Plumbing L2 – Plastic Pipe and Tubing
3. A PEX-B crimp ring fails the go/no-go gauge because the no-go gauge slides over it. What does this indicate?
NCCER Plumbing L1 – Plumbing Safety
4. Which fire safety item must be within arm's reach any time a torch is used in a lab or field setting?
NCCER Plumbing L2 – Copper Pipe and Fittings
5. Why must flux residue be wiped from a copper solder joint while it is still warm?
NCCER Plumbing L3 – Testing and Inspection
6. During a 100 psi, 5-minute air test, the pressure gauge drops from 100 psi to 100 psi with no movement. What is the correct interpretation?
NCCER Plumbing L2 – Plastic Pipe and Tubing
7. In a PEX-A expansion joint, after the pipe end and ring are expanded and the fitting barb is fully inserted, what causes the joint to tighten over time?
NCCER Plumbing L1 – Plumbing Safety
8. A student is preparing to modify an existing water supply line in a building. Before cutting into the live pipe, which safety procedure is required?
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