Plumber Pipe Installation & Repair Flashcards
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What is the purpose of a dielectric union when connecting copper pipe to a steel water heater?
Answer: To prevent galvanic corrosion between dissimilar metals
A dielectric union contains an insulating plastic sleeve and gasket that electrically isolates dissimilar metals to prevent galvanic corrosion.
A plumber discovers that a section of cast iron drain pipe has deteriorated and needs replacement. Which modern pipe material is the approved substitute for replacing sections of cast iron DWV pipe?
Answer: PVC Schedule 40
PVC Schedule 40 is the most common code-approved material for replacing cast iron DWV piping in residential and light commercial applications.
When installing ABS plastic drain pipe, which solvent cement must be used?
Answer: ABS-specific black solvent cement
ABS pipe requires ABS-specific black solvent cement; using PVC cement on ABS produces a weak joint that may fail under normal use.
What is the correct method for supporting vertical cast iron soil pipe at each floor level?
Answer: Install a riser clamp below the hub or above the coupling
Riser clamps installed below the hub bear the weight of vertical cast iron stacks and are required at each floor level.
Which pipe material must never be used for potable water distribution due to documented health risks?
Answer: Polybutylene (PB)
Polybutylene (PB) pipe was banned from potable water use because it degrades when exposed to oxidants in water, leading to catastrophic failures.
A drain pipe is backing up intermittently in a two-story building. The problem occurs only on the second floor. What is the most likely cause?
Answer: Partial blockage or insufficient venting in the second-floor branch line
Intermittent backups isolated to one floor typically indicate a partial blockage or venting problem in that floor's branch drain line.
What is the minimum clearance required between parallel hot and cold water supply pipes to prevent heat transfer between them?
Answer: 1/2 inch
A minimum of 1/2-inch clearance between hot and cold supply pipes reduces heat transfer that can warm cold water or cool hot water.