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NASCLA Commercial General Building Contractor — Practice Exam

Mechanical and plumbing: practice questions

Our NASCLA Commercial GC bank has 16 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.

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Question 1

What does a fire damper in ductwork do?

  1. Balances airflow between the supply and return ducts in each zone
  2. Controls room temperature
  3. Closes automatically to block fire spread through a rated wall or floor
  4. Filters smoke from air
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C. Closes automatically to block fire spread through a rated wall or floor — Access panels allow inspection and reset.

Question 2

Why are plumbing drain systems vented?

  1. To add water pressure
  2. To protect trap seals and let drains flow freely
  3. To heat the pipes
  4. To remove water vapor from rooms and keep the bathroom from fogging up
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B. To protect trap seals and let drains flow freely — Vents equalize air pressure in the drainage system.

Question 3

What does a pressure test on new water piping confirm?

  1. The pipe's color code and the labels on each line in the building
  2. The fixture flow rates
  3. The water temperature
  4. That the piping holds pressure without leaks before it is concealed
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D. That the piping holds pressure without leaks before it is concealed — Inspectors often witness the test.

Question 4

What safety device is required on a tank-type water heater?

  1. A temperature and pressure relief valve
  2. A backflow preventer only
  3. A pressure-reducing valve only
  4. A water hammer arrestor on the cold-water inlet line
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A. A temperature and pressure relief valve — Its discharge pipe must run to an approved location.

Question 5

Under the 2010 ADA Standards, how high may the front of an accessible lavatory rim be?

  1. 30 inches maximum
  2. 34 inches maximum above the floor
  3. 42 inches maximum above the finished floor surface
  4. 38 inches maximum
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B. 34 inches maximum above the floor — Knee and toe clearance is also required (ADA 606.3).

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