Question 1

What is the minimum liquid seal depth required for a fixture trap according to the IPC?

Accepted Answer

IPC 1002.1 requires a trap seal of not less than 2 inches and not more than 4 inches.

Question 2

Which type of trap is prohibited by the IPC?

Accepted Answer

IPC 1002.3 prohibits S-traps because they are prone to self-siphonage, which can break the trap seal.

Question 3

The maximum vertical distance from the fixture outlet to the trap weir is:

Accepted Answer

IPC 1002.1 states that the vertical distance from the fixture outlet to the trap weir shall not exceed 24 inches to prevent excessive velocity that could siphon the trap.

Question 4

A trap primer is required for:

Accepted Answer

IPC 1002.4 requires trap seals of emergency floor drains and other traps subject to evaporation to be protected by a trap seal primer or other approved method.

Question 5

According to IPC Table 1002.2, what is the maximum length of a trap arm for a 1-1/2 inch trap?

Accepted Answer

IPC Table 1002.2 limits the trap arm length (distance from trap to vent) for a 1-1/2 inch pipe to 6 feet.

Question 6

Under the UPC, the maximum horizontal distance for a 2-inch trap arm is:

Accepted Answer

UPC Table 1002.2 allows a maximum of 5 feet for a 2-inch trap arm. (Note the difference from IPC which allows 8 feet).

Question 7

Cleanouts shall be the same size as the pipe served up to ___ inches.

Accepted Answer

IPC 708.1.5 states cleanouts shall be the same nominal size as the pipe they serve, up to 4 inches. For pipes larger than 4 inches, the cleanout must be at least 4 inches.

Question 8

What is the minimum clearance required in front of a cleanout for a 2-inch pipe?

Accepted Answer

IPC 708.1.10.1 requires a minimum clearance of 12 inches in front of cleanouts installed on piping 2 inches or smaller in diameter. For larger pipes (3 inches through 6 inches), the required clearance increases to 18 inches. This clearance ensures that service technicians can access the cleanout with standard tools.

Question 9

Building sewers 8 inches and larger shall have a manhole installed at every change of direction and at intervals of not more than:

Accepted Answer

IPC 708.1.3: Manholes shall be installed at every change of grade, change of direction, and at intervals of not more than 400 feet for sewers 8 inches or larger.

Question 10

A trap with a seal greater than 4 inches is classified as:

Accepted Answer

IPC 1002.1 sets the maximum trap seal at 4 inches. Traps with deeper seals are generally prohibited unless specifically approved for special conditions (like high evaporation risk).

Question 11

Which of the following fixtures is allowed to have an integral trap?

Accepted Answer

Water closets and urinals have integral traps molded into the china fixture itself.

Question 12

In the IPC, a 'Drum Trap' is:

Accepted Answer

IPC 1002.3 lists drum traps as prohibited traps.

Question 13

A fixture trap must be:

Accepted Answer

IPC 1002.4 requires fixture traps to be self-cleaning (except for grease interceptors, etc.).

Question 14

Where is a cleanout required for a horizontal drainage pipe?

Accepted Answer

IPC 708.1.1 requires cleanouts at the upper terminal of the horizontal drainage piping (unless a fixture is nearby to access it).

Question 15

According to the IPC, the minimum size of a cleanout for a 3-inch pipe is:

Accepted Answer

IPC 708.1.5: Cleanouts must be the same size as the pipe served up to 4 inches. So a 3-inch pipe needs a 3-inch cleanout.

Question 16

Double trapping of a fixture is:

Accepted Answer

IPC 1002.1 prohibits double trapping because it causes air binding and flow restriction.

Question 17

What is the maximum distance between the fixture outlet and the trap for a commercial kitchen sink?

Accepted Answer

The 24-inch vertical distance limit applies to all fixtures, including commercial sinks, to prevent self-siphonage velocity.

Question 18

For a 3-inch trap, what is the maximum length of the trap arm (IPC)?

Accepted Answer

IPC Table 1002.2 allows a 12-foot trap arm for a 3-inch pipe.

Question 19

Which fitting can serve as a cleanout for a vertical stack?

Accepted Answer

A removable trap, a cleanout tee, or a two-way fitting are all acceptable means of accessing the pipe for cleaning.

Question 20

Under the UPC, a trap arm may not change direction more than ___ degrees without a cleanout.

Accepted Answer

UPC 1002.3 limits the total change in direction of a trap arm to 90 degrees without a cleanout.

Question 21

Grease traps (interceptors) must be equipped with a:

Accepted Answer

Grease interceptors require a flow control device to restrict the rate of flow so the grease has time to separate.

Question 22

Trap seals that are subject to evaporation must be protected by a trap seal primer or a:

Accepted Answer

IPC 1002.4 allows barrier type trap seal protection devices (like silicone flaps) as an alternative to water primers.

Question 23

A 'running trap' is generally prohibited except when used for:

Accepted Answer

Running traps are prohibited as fixture traps but may be allowed as a main building trap in some jurisdictions.

Question 24

What is the fall (slope) required for a trap arm?

Accepted Answer

Trap arms must be sloped at 1/4 inch per foot towards the vent.

Question 25

Cleanout plugs shall be made of:

Accepted Answer

Cleanout plugs must be brass or plastic to prevent rusting and seizing in the threads.

Question 26

The size of the cleanout for a 6-inch building sewer shall be at least:

Accepted Answer

IPC 708.1.5 requires cleanouts for pipes larger than 4 inches to be at least 4 inches in size.

Question 27

Which fixture is NOT required to have a trap?

Accepted Answer

All fixtures connected to the drainage system must be trapped to prevent sewer gas entry.

Question 28

Under the UPC, what is the maximum length of a trap arm for a 1-1/2 inch fixture drain?

Accepted Answer

UPC Table 1002.2 limits 1-1/2 inch trap arms to 42 inches (3' 6"). IPC allows 6 feet.

Question 29

Oil separators are required for:

Accepted Answer

Oil separators prevent flammable oils and gas from entering the sewer system in repair garages and similar facilities.

Question 30

Where a cleanout is installed on a concealed pipe, it must be:

Accepted Answer

Cleanouts must be accessible. Concealed piping cleanouts must be extended to the finished surface or have an access door.

Question 31

A 'Bell Trap' is:

Accepted Answer

Bell traps are prohibited because they rely on moving parts or seals that easily fail or evaporate.

Question 32

How much clearance is required above a cleanout installed in a floor slab?

Accepted Answer

Standard clearance for rodding is 18 inches vertically or horizontally depending on pipe size, but for floor cleanouts, vertical clearance is implied for the rodder machine.

Question 33

Traps shall be set true and level so as to:

Accepted Answer

If a trap is tilted, the water seal depth may be reduced, compromising protection against sewer gas.

Question 34

Can a two-way cleanout be used at a building drain/sewer junction?

Accepted Answer

A two-way cleanout allows rodding in both directions and satisfies the requirement for a cleanout at the junction.

Question 35

What is the maximum trap arm length for a 4-inch pipe in the IPC?

Accepted Answer

IPC Table 1002.2 sets the limit for a 4-inch trap arm at 16 feet.

Traps & Cleanouts Practice Questions

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