ILLINOIS STATE PLUMBING EXAM PRACTICE 2026|2027 QUESTIONS
AND ANSWERS WITH COMPLETE A+ SOLUTIONS!!!
What is the term for the measured length along the center line of the pipe and its fittings? - Correct
Answer -Developed Length
What fitting is acceptable for connecting 2 horizontal drain lines? - Correct Answer -Combination Wye and
1/8 Bend
What is the minimum vent size for a 4" trap? - Correct Answer -2"
What is required for a water piping system with a pressure exceeding 80 psi? - Correct Answer -
Pressure Reducing Valve
What is the minimum depth of a trap seal for any above ground plumbing fixture? - Correct Answer -2"
What is the minimum size of a gas and oil interceptor? - Correct Answer -6 Cubic Feet
What is the maximum distance allowed between trapped openings on a trench drains used to carry waste
to gas and oil interceptors? - Correct Answer -500 Square Feet
1|Page
,Water closet bowls for public use shall be of what design? - Correct Answer -Elongated, Plastic, Open-
Front
A bidet shall be equipped with what types of water? - Correct Answer -Hot and Cold, Tempered and Cold,
or Tempered Only
Where must a pump be installed on a whirlpool type bath tub? - Correct Answer -Above the weir of the
tub trap
Building sewers or sanitary sewers may only be installed within 10' of well when what type of piping is
installed? - Correct Answer -Cast Iron Pipe with Mechanical Joints or SCH40 PVC with Solvent Welded
Joints
What is the minimum pipe size of any combination waste and vent drainage line? - Correct Answer -4"
What is the primary function of the venting system? - Correct Answer -To protect trap seals from back-
pressure and siphonage
In what type of plumbing fixture may a magnesium rod be installed? - Correct Answer -Storage Type
Water Heater
2|Page
, All shower and shower/baths must be provided with what type of device? - Correct Answer -A
Thermostastic, Pressure Balance, or Combination Controlled Mixing Valve
Backflow devices must be installed in a way that they are protected from which conditions? - Correct
Answer -Freezing and Flooding
A protective strainer is required on the upstream side of the first check valve unless it is what type of
system? - Correct Answer -Fire Safety System
Which type of gas used in plumbing is lighter than air? - Correct Answer -Natural Gas
Piping, fixtures, or equipment installed in a way that interferes with normal operation of windows or
doors shall be: - Correct Answer -Relocated to avoid interference
What is the maximum interval between supports for a vertically installed cast iron pipe? - Correct Answer
-One Story Height
3|Page
AND ANSWERS WITH COMPLETE A+ SOLUTIONS!!!
What is the term for the measured length along the center line of the pipe and its fittings? - Correct
Answer -Developed Length
What fitting is acceptable for connecting 2 horizontal drain lines? - Correct Answer -Combination Wye and
1/8 Bend
What is the minimum vent size for a 4" trap? - Correct Answer -2"
What is required for a water piping system with a pressure exceeding 80 psi? - Correct Answer -
Pressure Reducing Valve
What is the minimum depth of a trap seal for any above ground plumbing fixture? - Correct Answer -2"
What is the minimum size of a gas and oil interceptor? - Correct Answer -6 Cubic Feet
What is the maximum distance allowed between trapped openings on a trench drains used to carry waste
to gas and oil interceptors? - Correct Answer -500 Square Feet
1|Page
,Water closet bowls for public use shall be of what design? - Correct Answer -Elongated, Plastic, Open-
Front
A bidet shall be equipped with what types of water? - Correct Answer -Hot and Cold, Tempered and Cold,
or Tempered Only
Where must a pump be installed on a whirlpool type bath tub? - Correct Answer -Above the weir of the
tub trap
Building sewers or sanitary sewers may only be installed within 10' of well when what type of piping is
installed? - Correct Answer -Cast Iron Pipe with Mechanical Joints or SCH40 PVC with Solvent Welded
Joints
What is the minimum pipe size of any combination waste and vent drainage line? - Correct Answer -4"
What is the primary function of the venting system? - Correct Answer -To protect trap seals from back-
pressure and siphonage
In what type of plumbing fixture may a magnesium rod be installed? - Correct Answer -Storage Type
Water Heater
2|Page
, All shower and shower/baths must be provided with what type of device? - Correct Answer -A
Thermostastic, Pressure Balance, or Combination Controlled Mixing Valve
Backflow devices must be installed in a way that they are protected from which conditions? - Correct
Answer -Freezing and Flooding
A protective strainer is required on the upstream side of the first check valve unless it is what type of
system? - Correct Answer -Fire Safety System
Which type of gas used in plumbing is lighter than air? - Correct Answer -Natural Gas
Piping, fixtures, or equipment installed in a way that interferes with normal operation of windows or
doors shall be: - Correct Answer -Relocated to avoid interference
What is the maximum interval between supports for a vertically installed cast iron pipe? - Correct Answer
-One Story Height
3|Page
