Question 1

Which PEX manufacturing method produces the most flexible tubing, with the highest degree of cross-linking and essentially no coil memory?

Accepted Answer

PEX-A is made by the peroxide (Engel) method, giving the highest cross-linking, the most flexibility, and no coil memory. A kink in PEX-A can even be repaired with a heat gun.

Question 2

PEX-A tubing is typically joined using which fitting system?

Accepted Answer

PEX-A uses cold-expansion fittings: the tubing and an expansion ring are stretched and then shrink back tightly over the fitting. PEX-B/C more commonly use insert crimp or clamp fittings.

Question 3

PEX-B tubing is most commonly joined using:

Accepted Answer

PEX-B is stiffer with more coil memory and is typically joined with copper crimp rings or stainless clamp (cinch) rings over an insert fitting.

Question 4

Which type of copper water tube has the thickest wall and is used for underground and higher-pressure applications?

Accepted Answer

Wall thickness ranks Type K (thickest) > Type L > Type M > DWV (thinnest, drainage only). Type K is used underground and for high-pressure service.

Question 5

Type L copper tube is identified by which color printed marking?

Accepted Answer

Copper tube color codes: Type K = green, Type L = blue, Type M = red, DWV = yellow.

Question 6

Which piping material is listed for hot-water distribution?

Accepted Answer

CPVC (chlorinated PVC) is rated for hot water. Standard PVC is for cold water and DWV only and must never be used for hot-water distribution; ABS and cast iron are DWV materials.

Question 7

Rigid white PVC pipe is commonly approved for which application?

Accepted Answer

PVC is used for DWV and cold-water service. It is not approved for hot water (use CPVC) or fuel gas.

Question 8

Hubless (no-hub) cast iron pipe is joined using:

Accepted Answer

No-hub cast iron is joined with a neoprene gasket and a stainless-steel shielded clamp (no-hub coupling) tightened to a specified torque.

Question 9

When connecting copper pipe directly to galvanized steel pipe, which fitting is used to prevent galvanic corrosion?

Accepted Answer

Dissimilar metals (copper and steel) in contact with water create a galvanic cell that corrodes the steel. A dielectric union separates the metals to prevent this.

Question 10

Why should PEX tubing not be installed exposed to direct sunlight or used outdoors uncovered?

Accepted Answer

PEX is sensitive to UV light; prolonged sunlight exposure breaks down the polymer. Most manufacturers limit allowable UV exposure to a number of months and prohibit permanent outdoor exposed use.

Question 11

As the water temperature in a PEX or CPVC system increases, the maximum allowable pressure rating of the pipe:

Accepted Answer

Plastic piping is rated by temperature and pressure together (e.g., PEX is commonly rated ~160 psi at 73°F but only ~100 psi at 180°F). As temperature rises, the allowable working pressure goes down.

Question 12

CPVC pipe and fittings are joined using:

Accepted Answer

CPVC must be joined with solvent cement formulated for CPVC. Using standard PVC cement on CPVC is not approved and can lead to joint failure.

Piping Materials (PEX, Copper, CPVC) Practice Questions

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