Question 1

According to the IPC, what is the drainage fixture unit (DFU) value for a residential water closet (1.6 gpf or less)?

Accepted Answer

IPC Table 709.1 assigns a value of 3 DFU to a water closet (flush tank, 1.6 gpf or less). Older or higher flow toilets are rated at 4 DFU.

Question 2

What is the minimum required slope for a 3-inch horizontal drainage pipe?

Accepted Answer

IPC Section 704.1 requires a minimum slope of 1/4 inch per foot for pipe sizes of 2-1/2 inches or less and 3 to 6 inches. 1/8 inch per foot is allowed for pipes 8 inches or larger.

Question 3

What is the maximum distance allowed between cleanouts on a horizontal building drain?

Accepted Answer

Cleanouts shall be installed not more than 100 feet apart in horizontal drainage lines.

Question 4

Under the UPC, what is the Drainage Fixture Unit (DFU) value for a domestic kitchen sink?

Accepted Answer

UPC Table 702.1 assigns a value of 2.0 DFU to a domestic kitchen sink (with or without dishwasher connection).

Question 5

A horizontal branch drain needs to carry a load of 24 DFU. According to IPC Table 710.1(2), what is the minimum required pipe diameter?

Accepted Answer

IPC Table 710.1(2) states that a 3-inch horizontal branch allows a maximum of 20 DFU. Therefore, the size must be increased to 4 inches, which allows up to 160 DFU.

Question 6

What is the DFU value for a residential bathtub?

Accepted Answer

A bathtub (with or without overhead shower) is assigned 2 DFU in IPC Table 709.1.

Question 7

According to the IPC, cleanouts are required at each change of direction greater than:

Accepted Answer

A cleanout is required at each change of direction of the piping that is greater than 45 degrees.

Question 8

Calculate the total DFU load for a bathroom group consisting of one water closet (1.6 gpf), one lavatory, and one bathtub.

Accepted Answer

IPC Table 709.1 Note f allows a bathroom group to be calculated differently, but typically individually: WC (3) + Lav (1) + Tub (2) = 6 DFU. However, referencing Table 710.1(2) note regarding bathroom groups, the IPC typically assigns a Bathroom Group value of 5 DFU for sizing stacks/branches if using the group method.

Question 9

What is the minimum size of a building drain serving a single water closet?

Accepted Answer

IPC Section 710.1.1 states that the minimum size of a horizontal drainage pipe receiving the discharge of a water closet shall be 3 inches.

Question 10

Under the UPC, drainage piping 4 inches or larger must have a minimum slope of:

Accepted Answer

UPC Section 708.0 allows horizontal drainage piping of 4 inches or larger to be installed with a slope of not less than 1/8 inch per foot where structural conditions require.

Question 11

Which of the following fittings is NOT permitted for a change in direction from vertical to horizontal flow?

Accepted Answer

Sanitary tees are permitted for flow from horizontal to vertical, but NOT vertical to horizontal (obstruction hazard). You must use a wye, long sweep, or combination.

Question 12

What is the minimum clearance required in front of a cleanout for pipes 3 inches and larger?

Accepted Answer

IPC Section 708.1.10.2 requires a minimum clearance of 18 inches for cleanouts on piping 3 inches to 6 inches.

Question 13

In the IPC, what is the maximum number of drainage fixture units allowed on a 2-inch horizontal fixture branch?

Accepted Answer

According to IPC Table 710.1(2), a 2-inch horizontal fixture branch is limited to 6 drainage fixture units.

Question 14

A sump pump discharge pipe must have which of the following installed?

Accepted Answer

A check valve and a full-open valve (gate or ball valve) shall be installed in the pump discharge piping to prevent backflow and allow service.

Question 15

What is the DFU value for a 3-inch floor drain?

Accepted Answer

Under the UPC Table 702.1, a floor drain with a 3-inch trap is assigned 4 drainage fixture units (DFU). This value is used when calculating the total DFU load on a drainage system. Note that IPC Table 709.1 may assign different values, so always confirm which code applies in your jurisdiction.

Question 16

Copper tubing used for drainage (DWV) must be at least Type:

Accepted Answer

Copper tube for drainage, waste, and vent applications can be Type DWV (yellow), which has thinner walls than M, L, or K.

Question 17

According to the UPC, what is the maximum number of DFUs allowed on a 3-inch building drain with a 1/4 inch per foot slope?

Accepted Answer

UPC Table 703.2 limits a 3-inch horizontal building drain sloped at 1/4 inch per foot to a maximum of 35 drainage fixture units. The IPC permits significantly higher DFU loads on a 3-inch drain, making this a key code difference that exam candidates should know when working under the UPC.

Question 18

Double sanitary tees may be used for:

Accepted Answer

Double sanitary tees are permitted for connecting back-to-back fixtures (like toilets) to a vertical stack, provided the barrel size is at least 2 pipe sizes larger than the inlet for blow-out fixtures, but generally allowed for horizontal-to-vertical inlet flow.

Question 19

Indirect waste pipes must discharge into the building drainage system through a(n):

Accepted Answer

Indirect waste pipes (e.g., from food prep sinks) must discharge through an air gap or air break to prevent cross-contamination.

Question 20

What is the DFU value for a clothes washer standpipe?

Accepted Answer

IPC Table 709.1 assigns 2 DFU to a clothes washer standpipe.

Question 21

A 4-inch horizontal drainage pipe with a slope of 1/8 inch per foot can carry a maximum of how many DFUs?

Accepted Answer

Under IPC Table 710.1(1), a 4-inch pipe at 1/8 inch slope carries 180 DFU. (At 1/4 inch slope, it carries 216 DFU).

Question 22

The annular space between the pipe and the sleeve where a pipe passes through a foundation wall shall be filled with:

Accepted Answer

The space needs to be sealed to prevent entry of rodents and moisture, but usually not rigidly cemented to the pipe to allow for settling.

Question 23

In the IPC, a stack is defined as a vertical line of soil, waste, or vent piping extending through at least:

Accepted Answer

A stack is defined as a general term for any vertical line of soil, waste, vent, or inside conductor piping that extends through at least one story with or without offsets.

Question 24

Grease interceptors are required for:

Accepted Answer

Grease interceptors are required in commercial food processing areas where grease can be introduced into the drainage system.

Question 25

You are plumbing a small office building. You have a stack serving 3 floor drains (2 inch) and 2 lavatories. What is the total DFU load?

Accepted Answer

Floor drain (2") = 2 DFU each x 3 = 6 DFU. Lavatory = 1 DFU each x 2 = 2 DFU. Total = 8 DFU.

Question 26

According to IPC 2024, what is the maximum length of a 2-inch trap arm?

Accepted Answer

IPC Table 1002.2 states the maximum trap arm length for a 2-inch pipe is 8 feet.

Question 27

Solvent cement joints for PVC pipe require the use of:

Accepted Answer

PVC solvent cementing requires a purple primer to prepare the surface, unless specific non-primer cements are approved for non-pressure applications up to 4 inches (depending on local code amendments). Standard code usually mandates primer.

Question 28

What is the minimum size for a drainage pipe underground (buried) according to the UPC?

Accepted Answer

UPC Section 703.1 states that no portion of the drainage system installed underground or below a basement or cellar shall be less than 2 inches in diameter.

Question 29

A fixture trap must be protected against siphonage and backpressure by a:

Accepted Answer

The primary purpose of a vent system is to protect the trap seal from siphonage and backpressure.

Question 30

Chemical waste systems must be:

Accepted Answer

Chemical waste that is detrimental to the sewer system must be treated/neutralized and is often required to be a separate system until treated.

Question 31

According to the IPC, the minimum trap size for a shower is:

Accepted Answer

IPC Table 709.1 requires a minimum trap size of 1-1/2 inches for a shower.

Question 32

Under the UPC, drainage pipe cleanouts must be designed to open to allow cleaning in:

Accepted Answer

UPC 707.5 requires cleanouts to be installed so that the cleanout opens to allow cleaning in the direction of flow of the soil or waste.

Question 33

A macerating toilet system is typically used when:

Accepted Answer

Macerating toilet systems pump waste up to the gravity sewer line when gravity flow is not possible.

Question 34

What is the minimum diameter of a standpipe receptor for a clothes washer?

Accepted Answer

IPC Section 802.4.3 requires the standpipe to be a minimum of 2 inches in diameter.

Question 35

Using IPC Table 710.1(1), determine the maximum DFUs allowed on a 3-inch building drain sloped at 1/8 inch per foot.

Accepted Answer

IPC Table 710.1(1) indicates that a 3-inch pipe slope is not permitted at 1/8 inch per foot. 3-inch pipes generally require 1/4 inch per foot minimum.

Question 36

Cast iron soil pipe supports for horizontal runs should be spaced not more than:

Accepted Answer

IPC Table 308.5 requires cast iron soil pipe to be supported every 5 feet horizontally, except where 10-foot lengths are used.

Question 37

Which material is prohibited for use in chemical waste systems unless specifically approved?

Accepted Answer

Copper is susceptible to corrosion from many chemicals and acids found in chemical waste systems.

Question 38

Under the IPC, what is the maximum DFU load for a 2-inch vertical stack?

Accepted Answer

IPC Table 710.1(2) allows a maximum of 10 DFU on a 2-inch stack (provided it is not more than 3 stories high).

Question 39

Cleanouts on 6-inch and smaller pipes shall be provided with a clearance of not less than ___ inches for rodding.

Accepted Answer

IPC 708.1.10.2: For pipes 3 to 6 inches, the required clearance is 18 inches.

Question 40

A drinking fountain has a DFU value of:

Accepted Answer

IPC Table 709.1 assigns 0.5 DFU to a drinking fountain.

Question 41

The drainage system of a building needs to be tested with water. The water level must be no less than ___ feet above the highest fitting being tested.

Accepted Answer

IPC 312.2 requires a water test with a 10-foot head of water.

Question 42

A backwater valve is required when:

Accepted Answer

IPC 715.1 requires backwater valves for fixtures installed on a floor below the elevation of the next upstream manhole cover to prevent sewage backup.

Question 43

Which of the following is an acceptable joint for joining plastic pipe to cast iron pipe?

Accepted Answer

Transition fittings such as shielded couplings (Fernco/No-Hub type) are required for joining dissimilar piping materials like plastic and cast iron.

Question 44

According to the IPC, what is the minimum trap size for a commercial food waste grinder?

Accepted Answer

IPC Table 709.1 lists 'Food waste grinder, commercial' with a minimum trap size of 2 inches.

Question 45

Under the UPC, a clothes washer standpipe must extend above the trap weir a minimum of ___ inches.

Accepted Answer

UPC 804.1 requires that a clothes washer standpipe extend at least 18 inches above the trap weir, and not more than 30 inches above the floor. The 18-inch minimum ensures adequate air space above the washing machine's drain hose connection to prevent backflow. The maximum height prevents excessive vacuum conditions.

Question 46

What is the maximum DFU load for a 3-inch horizontal branch drain in the IPC?

Accepted Answer

IPC Table 710.1(2) sets the maximum DFU for a 3-inch horizontal branch at 20.

Question 47

A 'Continuous Waste' arrangement is most commonly seen on:

Accepted Answer

Continuous waste refers to the piping connecting multiple sink bowls to a single trap.

Question 48

Using IPC Table 709.1, calculate the DFUs for a renovation adding: 2 lavatories, 2 water closets (1.6 gpf), and 1 drinking fountain.

Accepted Answer

Lavatories: 2 x 1 = 2 DFU. WCs: 2 x 3 = 6 DFU. Drinking Fountain: 1 x 0.5 = 0.5 DFU. Total = 8.5 DFU.

Question 49

Horizontal drainage piping shall be installed in practical alignment and a uniform slope. What is the exception where a lesser slope is allowed?

Accepted Answer

The code allows a slope of 1/8 inch per foot for piping 4 inches or larger if structural conditions preclude a 1/4 inch slope, provided approved by the code official.

Question 50

For a 1-1/4 inch fixture drain, what is the maximum developed length of the trap arm according to IPC Table 1002.2?

Accepted Answer

IPC Table 1002.2 states the max trap arm length for 1-1/4 inch pipe is 5 feet.

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