UTILITIES | Plumbing Systems | 15 Questions (EASY-MODERATE)

PLUMBING SYSTEMS

(15 Questions, Difficulty Level: EASY to MODERATE)

by Raison John J. Bassig

Q#1: How do you measure the seal of a trap?
a. From crown weir to top of dip
b. From invert to end of trap arm
c. Seal is equal to the pipe diameter and its attached trap
d. From crown weir to bottom of dip

The depth of a trap seal is measured from the "lowest point in the cross-section of the horizontal waterway at the exit of the trap" (i.e., crown weir) to the "lowest portion of the inside top surface of the channel through the trap" (i.e., dip), as shown:

Therefore, the correct answer is a. From crown weir to top of dip.

Q#2: A valve in which the flow of fluid is cut off by means of a circular disc that fits over and against the horizontal valve seat.
a. Butterfly Valve
b. Globe Valve
c. Gate Valve
d. Shut-Off Valve

Butterfly Valves regulate the flow of fluid by means of a rotating disc to open or close the passageway.

Globe Valves control the flow rate of fluids by means of a circular disc fitted over and against a horizontal seat.

Gate Valves cut off the flow of fluid by means of a wedge-disc at right angles to the direction of flow.

A shut-off valve is a general term used for any valve that can terminate the flow of fluid in a system. So, all the valves in the choices are actually types of shut-off valves as they can cut off the flow of fluid. Note that NOT all valves can terminate the flow, for example, check valves, foot valves, pressure reducing valves, etc.

The primary difference between the Globe Valve and the Gate valve is how their discs are oriented. The Globe Valves have this disc parallel to the flow, while the Gate Valves have this disc perpendicular to the flow. As such, Globe Valves have that extra feature of being able to regulate/control the flow of fluid by varying the height of the disc above the horizontal valve seat for a partially-open/close position. On the other hand, Gate Valves do NOT have this feature as these valves must only be either in a fully-closed or fully-opened position (as the disc may become damaged or may erode over time if partially left open since it is perpendicular to the flow of fluid).

Therefore, the correct answer is b. Globe Valve.

Q#3: What pipe size would you specify for an individual vent pipe serving a 6" (152mm) diameter drain?
a. 1-1/4" (32mm)
b. 2" (51mm)
c. 3" (76mm)
d. 4" (102mm)

According to the 1999 Revised National Plumbing Code of the Philippines (RNPCP), which was based on the 1997 Uniform Plumbing Code (UPC), on Size of Vents,

"...xxx...The diameter of an individual vent shall not be less than one and one-fourth (1-1/4) inches (32mm) nor less than one-half (1/2) the diameter of the drain to which it is connected."
(Sec. 910.1 of the 1999 RNPCP, and Sec. 904.1 of the 1997 UPC)

As the drain size in my question is given at 6" (152mm), then, per code, the vent size diameter shall be either:

32mm
or
1/2 of [drain diameter] = 1/2 x [152mm] = 76mm

Since we are looking for the MINIMUM size, then, the HIGHER value (76mm) is the more strigent to conform with code provisions.

Therefore, the correct answer is c. 3" (76mm).

Q#4: An outhouse or structure used for the deposition of excrement.
a. Latrine
b. Seepage Pit
c. Privy
d. Leaching Cesspool

By definition, as per 1999 Revised National Plumbing Code of the Philippines (RNPCP),

"LATRINE - a water closet consisting of a continuous trough containing water.  The trough extends under two or more adjacent seats.  Prohibited by health authorities for permanent installations."
(Sec. 213.3 of the 1999 RNPCP)

"SEEPAGE PIT - a loosely lined excavation in the ground, which receives the discharge of a septic tank and design to permit the effluent from the septic tank to seep through pit bottom and sides."
(Sec. 220.6 of the 1999 RNPCP)

"PRIVY - an outhouse or structure used for the deposition of excrement."
(Sec. 217.21 of the 1999 RNPCP)

"LEACHING CESSPOOL - a cesspool that is not watertight."
(Sec. 213.5 of the 1999 RNPCP)

Therefore, the correct answer is c. Privy.

Q#5: A water supply pipe which extends vertically one full story or more to convey water to branches or to a group of fixtures.
a. Stack
b. VSTR
c. Branch
d. Riser

Stack is a term used for DWV (Drain-Waste-Vent) Systems describing a pipe that is vertical.

VSTR is an acryonym for "Vent Stack Through Roof" describing the portion of the vertical vent pipe that extends all the way past the roof line to access natural ventilation.

Branch is a term used for both DWV and Water Distribution systems describing a pipe that is horizontal (or slightly horizontal with a certain slope in the case of DWV).

Riser is a term used for Water Distribution Systems (as well as in Electrical Distribution Systems) describing a pipe (or conduit) that is vertical.

Therefore, the correct answer is d. Riser.

Q#6: The extension to the open air of a soil or waste stack above the highest horizontal branch drain connected to the stack for purposes of venting the drainage system.
a. Relief Vent
b. Vent Stack
c. Circuit Vent
d. Stack Vent

By definition, as per 1999 Revised National Plumbing Code of the Philippines (RNPCP),

"RELIEF VENT - a vertical vent line, the primary function of which is to provide additional circulation of air between the drainage and vent systems or to act as an auxiliary vent on a specially designed system such as a "yoke vent" connection between the soil and vent stacks."
(Sec. 219.3 of the 1999 RNPCP)

"VENT STACK - the vertical vent pipe installed primarily for providing circulation of air to and from any part of the soil, waste of the drainage system."
(Sec. 223.4 of the 1999 RNPCP)

"CIRCUIT VENT - a group of vent pipe which starts in front of the extreme fixture connection on a horizontal branch and connects to the vent stack."
(Sec. 204.8 of the 1999 RNPCP)

"STACK VENT - the extension of a soil or waste stack above the highest horizontal drain connected to the stack.  The uppermost end above the roof is called the stack vent through roof (SVTR)."
(Sec. 220.31 of the 1999 RNPCP)

Most are confused and erronously interchage the terms "Vent Stack" and "Stack Vent". As can be determined in their definitions, a STACK VENT is an EXTENSION ABOVE the actual SOIL/WASTE STACK, meaning, it is the SAME PIPE as the soil/waste stack below it, only that, the portion below the highest horizontal drain connecting to THAT PIPE will convey fecal/wastewater (the soil/waste stack) while the portion above such drain will only convey air (the stack vent).

In other words, the Soil/Waste STACK has a VENT above it, thus the term, "STACK VENT" (or the "vent of the stack").

On the other hand, a VENT STACK can be ANY VERTICAL PIPE that only acts as a vent for the fixtures, or for the branches, or even for the soil/waste stack. So, the Vent Stack is NOT the same pipe as the soil/waste stack. A Vent Stack, often exclusively conveys air (unless such a Vent Stack was designed as a Wet Vent, allowing on limited occassions for wastewater to pass through).

In other words, as there is a term called 'Vent Branch' describing a "Vent Pipe" that is "Horizontal", then, the Vent STACK just simply describes a "Vent Pipe" that is "Vertical", thus the term, "VENT STACK" (or "vent that is vertical").

Therefore, the correct answer is d. Stack Vent.

Q#7: What type of water closet has its trapway located in front?
a. Siphon Vortex
b. Blow-out
c. Wash-down
d. Reverse-Trap

Among all common types of water closets, only the wash-down type has its trapway located in front.  Later on, this was reversed in a more efficient design to the rear with the reverse-trap type.  Here are illustrations of the different types of water closets:

Therefore, the correct answer is c. Wash-Down.

Q#8: If the house sewer is 6" and inclined at 2%, what is the maximum drainage fixture units for the building served?
a. 600 Fixture Units
b. 610 Fixture Units
c. 580 Fixture Units
d. 720 Fixture Units

According to the 1999 Revised National Plumbing Code of the Philippines (RNPCP), which was based on the 1997 Uniform Plumbing Code (UPC), on Maximum Fixture Unit Loading,

(Table 7-5 of the 1999 RNPCP, and Table 7-5 of the 1997 UPC)

Therefore, the correct answer is d. 720 Fixture Units.

Q#9: Minimum trap and trap arm size diameter of a "sitz" bath?
a. 1-1/2"
b. 2"
c. 3"
d. 4"

Note that a "sitz" bath is more commonly known as a Bidet, which was also defined in the 1999 Revised National Plumbing Code of the Philippines (RNPCP),

"BIDET - A plumbing fixtures used for washing the middle private parts of the body, especially the genitals.  Also called a "sitz" bath."
(Sec. 203.15 of the 1999 RNPCP)

As per code, on Minimum Trap Diameters and Drainage Fixture Unit Values,

(Table 7-2 of the 1999 RNPCP)

Therefore, the correct answer is a. 1-1/2" (or 38mm).

Q#10: In hospital ward rooms, what is the minimum water closet fixtures per patient?
a. 1 water closet per 25 patients
b. 1 water closet per 10 patients
c. 1 water closet per 40 patients
d. 1 water closet per 8 patients

According to the 1999 Revised National Plumbing Code of the Philippines (RNPCP), which was based on the 1997 Uniform Plumbing Code (UPC), on Minimum Plumbing Facilities,

(Table 4-1 of the 1999 RNPCP, and Table 4-1 of the 1997 UPC)

Therefore, the correct answer is d. 1 water closet per 8 patients.

Q#11: You specified to use a 3" (76mm) PVC pipe size for the waste stack in the building you are designing. What is the maximum vertical length of the waste stack?
a. 20m
b. 45m
c. 65m
d. Unlimited

According to the 1999 Revised National Plumbing Code of the Philippines (RNPCP), which was based on the 1997 Uniform Plumbing Code (UPC), on Maximum Fixture Unit Loading and Maximum Length of Excreta Drainage and Vent Piping,

(Table 7-5 of the 1999 RNPCP, and Table 7-5 of the 1997 UPC)

Therefore, the correct answer is c. 65m (or 212 feet).

Q#12: Sizing vertical rainwater piping is based upon the maximum depth of rainfall per hour falling upon a given roof area. Normally, the rainfall intensity used around the areas in Manila is ______.
a. 204mm / hour rainfall
b. 102mm / hour rainfall
c. 51mm / hour rainfall
d. 8mm / hour rainfall

According to the 1999 Revised National Plumbing Code of the Philippines (RNPCP),

"Vertical rainwater piping shall be sized in accordance with Table 11-1, which is based upon maximum depth in mm or rainfall per hour falling upon a given roof area in square meter. Consult local rainfall figures to determine maximum rainfall per hour. Normally, a 102 MM/HOUR RAINFALL intensity is used around MANILA area."
(Sec. 1104.1 of the 1999 RNPCP)
(See also Sec. 1104.4 for an example, and the Notes ** in Table 11-1 of the 1999 RNPCP)

Therefore, the correct answer is b. 102mm / hour rainfall.

Q#13: What is the minimum trap arm size diameter of a Pedestal Urinal?
a. 1-1/2"
b. 2"
c. 3"
d. 1-1/4"

According to the 1999 Revised National Plumbing Code of the Philippines (RNPCP), on Minimum Trap Diameters and Drainage Fixture Unit Values,

(Table 7-2 of the 1999 RNPCP)

So, categorizing each type of urinal by trap arm sizes (for ease of familiarizing):

3" (or 76mm):
- Urinal, pedestal, trap arm only
- Urinal, wall-mounted, blowout, integral trap, trap arm only

2" (or 51mm):
- Urinal, stall, separate trap
- Urinal, wall-mounted, integral trap, trap arm only
- Urinal, wall-mounted, washdown, integral trap, trap arm only
- Urinal, wall-mounted, siphon jet, integral trap, trap arm only

1-1/2" (or 38mm):
- Urinal, wall-mounted, washout, separate trap 50.8mm min. waste

Therefore, the correct answer is c. 3" (or 76mm).

Q#14: Water distribution system where water is first delivered to an overhead tank before it is delivered to individual taps.
a. Up-feed
b. Down-feed
c. Air Pressure System
d. Hydro-pneumatic System

An Up-Feed System distributes the water from the main (as provided by the local water utility company), using normal pressure, directly to the individual taps, fixtures, or equipment.

A Down-Feed System (otherwise known as a Gravity System) distributes the water by first pumping into a water reservoir above (e.g., a tank) and is then distributed to the individual taps, fixtures, or equipment by means of gravity.

An Air Pressure System (or a Hydro-Pneumatic System) distributes the water via compressed air to raise pressure and push the water through the system.

Therefore, the correct answer is b. Down-feed.

Q#15: What would be the minimum number of Water Closets in the Male Toilets you must provide given a Theater with a projected 250-400 male patrons?
a. 1
b. 2
c. 3
d. 4

According to the 1999 Revised National Plumbing Code of the Philippines (RNPCP), which was based on the 1997 Uniform Plumbing Code (UPC), on Minimum Plumbing Facilities,

(Table 4-1 of the 1999 RNPCP, and Table 4-1 of the 1997 UPC)

Therefore, the correct answer is c. 3.