Journeyman Plumber ExamWater Supply SystemsHard
A plumber is installing a water service line from the public water main to a residential property. The trench passes through an area known to have aggressive soil conditions (e.g., highly acidic or alkaline). Which of the following water service pipe materials would be most resistant to external corrosion in such conditions?
- APVC (Polyvinyl Chloride) plastic pipe.
- BDuctile iron pipe.
- CType M copper tubing.
- DGalvanized steel pipe.
Show answer & explanationAnswer & explanation
Correct answer: A. PVC (Polyvinyl Chloride) plastic pipe.
Plastic pipes like PVC are inherently non-metallic and are therefore immune to electrochemical corrosion, which is the primary concern in aggressive soil conditions. While other materials might be protected with coatings or cathodic protection, PVC offers natural resistance.
Why the other options are wrong
- B. Ductile iron pipe is strong but is also a metallic pipe and requires special coatings or cathodic protection to resist corrosion in aggressive soils.
- C. Copper, while generally durable, can be susceptible to corrosion in highly aggressive soils, sometimes requiring protective coatings or sleeves.
- D. Galvanized steel is highly susceptible to external corrosion in aggressive soil, as the zinc coating wears away, exposing the steel.
Pipe Material Corrosion Resistance
The ability of a pipe material to withstand degradation due to chemical reactions with its environment, particularly relevant for underground installations in aggressive soil conditions.
- Metallic pipes are susceptible to electrochemical corrosion.
- Plastic pipes are generally immune to electrochemical corrosion.
- Soil pH, moisture, and resistivity affect corrosion rates.
Memory trick: Aggressive soil? Go plastic, it's fantastic, no rust to be drastic.