Journeyman Plumber ExamWater Supply SystemsMedium
A plumber is installing a water distribution system using PEX tubing. According to common plumbing codes, what is the maximum permissible continuous operating temperature for PEX tubing used in potable hot water systems?
- A200°F (93°C)
- B180°F (82°C)
- C160°F (71°C)
- D140°F (60°C)
Show answer & explanationAnswer & explanation
Correct answer: B. 180°F (82°C)
PEX tubing, specifically PEX-a, PEX-b, and PEX-c, is generally rated for a maximum continuous operating temperature of 180°F (82°C) at 100 psi, and often 200°F (93°C) for intermittent use. For continuous hot water systems, 180°F is the standard maximum.
Why the other options are wrong
- A. 200°F is typically the rating for intermittent or short-term exposure, not continuous operation.
- C. 160°F is below the maximum continuous operating temperature for PEX.
- D. 140°F is a common temperature for domestic hot water but not the maximum rating of PEX.
PEX Temperature Rating
The maximum continuous operating temperature for which PEX (cross-linked polyethylene) tubing is rated, typically 180°F (82°C) at 100 psi for potable hot water applications.
- PEX is resistant to high temperatures.
- Ratings include both temperature and pressure.
- Exceeding ratings can degrade material and cause failure.
Memory trick: PEX hot water: 180, don't let it run too high, you know.