CCI Plumbing & Mechanical Systems 2 — Questions and Answers
Question 1: What is the minimum slope required for horizontal drainage piping with a 3-inch diameter per the IPC?
- 1/16 inch per foot
- 1/8 inch per foot (Correct answer)
- 1/4 inch per foot
- 1/2 inch per foot
Correct answer: 1/8 inch per foot
The IPC requires 3-inch horizontal drainage pipes to slope at a minimum of 1/8 inch per foot toward the point of discharge.
Question 2: A pressure-reducing valve (PRV) is required when the water service pressure exceeds which threshold?
- 60 psi
- 80 psi (Correct answer)
- 100 psi
- 120 psi
Correct answer: 80 psi
Per the IPC, a PRV must be installed when the water supply pressure exceeds 80 psi to protect fixtures and piping.
Question 3: Which type of trap is prohibited under most modern plumbing codes?
- P-trap
- Drum trap
- Bottle trap
- S-trap (Correct answer)
Correct answer: S-trap
S-traps are prohibited because they can self-siphon, losing the water seal that prevents sewer gases from entering the building.
Question 4: During a hydrostatic pressure test on new water supply piping, what is the minimum test pressure and duration required by the IPC?
- 50 psi for 10 minutes
- 100 psi for 15 minutes (Correct answer)
- 150 psi for 15 minutes
- 200 psi for 30 minutes
Correct answer: 100 psi for 15 minutes
The IPC requires new water supply systems to be tested at 100 psi for a minimum of 15 minutes without leaking.
Question 5: What is the primary function of a backflow preventer in a plumbing system?
- Reduce water pressure spikes
- Prevent contaminated water from entering the potable supply (Correct answer)
- Increase flow velocity in supply lines
- Equalize pressure between hot and cold lines
Correct answer: Prevent contaminated water from entering the potable supply
A backflow preventer stops contaminated or non-potable water from reversing flow and entering the clean water supply due to back-pressure or back-siphonage.
Question 6: An inspector notices that a sanitary tee is installed horizontally in a drainage system. This is:
- Acceptable if flow is in the direction of the tee inlet
- Acceptable only for 2-inch or smaller pipe
- A code violation requiring correction (Correct answer)
- Acceptable if a cleanout is installed nearby
Correct answer: A code violation requiring correction
Sanitary tees must not be used in a horizontal position because they cause turbulence and solids buildup; a wye fitting must be used instead.
Question 7: What is the purpose of the air gap required at a plumbing fixture indirect waste connection?
- Reduce pipe vibration
- Prevent sewer gas odors
- Protect against backflow contamination (Correct answer)
- Allow for thermal expansion
Correct answer: Protect against backflow contamination
An air gap provides a physical break between the waste outlet and the flood level rim of the receptor, preventing backflow contamination of potable water.
CCI Plumbing & Mechanical Systems 2
What is the minimum slope required for horizontal drainage piping with a 3-inch diameter per the IPC?