Master Plumber Exam Philippines Master Plumber Code and Regulations 1 — Questions and Answers
Question 1: Under the National Plumbing Code of the Philippines (NPCP), what is the minimum trap seal depth required for fixture traps?
- 25 mm (1 inch)
- 38 mm (1.5 inches) (Correct answer)
- 50 mm (2 inches)
- 75 mm (3 inches)
Correct answer: 38 mm (1.5 inches)
The NPCP requires a minimum trap seal depth of 38 mm (1½ inches) to prevent sewer gases from entering the building.
Section 1002 of the National Plumbing Code of the Philippines specifies that every fixture trap shall have a liquid seal of not less than 38 mm (1½ inches) and not more than 100 mm (4 inches). This seal prevents sewer gases, which can be toxic and combustible, from passing through the trap and entering the occupied space. A seal shallower than 38 mm is susceptible to evaporation and siphonage, while a seal deeper than 100 mm may be subject to self-siphonage due to high water column weight.
Question 2: According to the Philippine Sanitation Code (PD 856), what is the minimum distance between a deep well and a septic tank?
- 10 meters
- 15 meters
- 20 meters
- 25 meters (Correct answer)
Correct answer: 25 meters
PD 856 requires a minimum horizontal distance of 25 meters between a deep well and a septic tank to prevent contamination of the water supply.
Presidential Decree No. 856 (Code on Sanitation of the Philippines) sets minimum horizontal clearances to protect potable water sources from contamination. A deep well must be at least 25 meters from a septic tank, 25 meters from an absorption field, and 50 meters from a cesspool or privy. These distances account for the lateral movement of effluent through soil and the time needed for biological purification. Shallow wells require even greater separation distances because they draw water from near-surface aquifers more susceptible to contamination.
Question 3: In the NPCP, what is the fixture unit (FU) value assigned to a lavatory (washbasin) for drainage load calculation?
- 1 FU (Correct answer)
- 2 FU
- 3 FU
- 4 FU
Correct answer: 1 FU
A lavatory is assigned 1 fixture unit for drainage load calculations under the NPCP.
The National Plumbing Code of the Philippines assigns Drainage Fixture Unit (DFU) values to each plumbing fixture based on its rate and duration of discharge. A lavatory (washbasin) is rated at 1 DFU, which represents the base unit of measurement. A bathtub or shower is 2 DFU, a water closet (toilet) is 4 DFU (public) or 3 DFU (private), and a floor drain is 2 DFU. These values are used to size drainage pipes, stacks, and building drains to handle the anticipated peak flow from all connected fixtures.
Question 4: What does 'PN6' designation mean for PVC pressure pipes used in water supply systems in the Philippines?
- Pipe Nominal diameter of 6 mm
- Pressure Nominal rating of 6 bar (600 kPa) (Correct answer)
- Philippine National Standard Grade 6
- Pipe Network classification 6
Correct answer: Pressure Nominal rating of 6 bar (600 kPa)
PN6 stands for Pressure Nominal 6 bar, meaning the pipe is rated for a maximum working pressure of 600 kPa (approximately 87 psi).
In accordance with Philippine National Standards (PNS) and ISO standards, the PN designation on pressure pipes indicates the Pressure Nominal rating, which is the maximum allowable operating pressure at 20°C in bar. PN6 pipes are rated for 6 bar (600 kPa or ~87 psi), suitable for low-pressure distribution mains and service connections. PN10 pipes handle 10 bar (1,000 kPa), used for medium-pressure distribution. PN16 pipes handle 16 bar (1,600 kPa), used for high-pressure mains. Higher PN ratings indicate thicker pipe walls and greater material strength. Selection depends on the system's static and dynamic pressure requirements.
Question 5: Under the NPCP, what is the maximum trap arm length (distance from trap weir to vent) for a 38 mm (1½-inch) drain pipe?
- 0.75 m (2.5 ft)
- 1.0 m (3.3 ft)
- 1.5 m (5 ft) (Correct answer)
- 1.8 m (6 ft)
Correct answer: 1.5 m (5 ft)
For a 38 mm diameter drain pipe, the maximum trap arm length is 1.5 m (approximately 5 feet) per the NPCP.
The National Plumbing Code of the Philippines limits trap arm lengths to prevent loss of the trap seal through induced siphonage. The allowable trap arm distance is measured from the trap weir (the crown of the trap) to the inner edge of the vent pipe. For a 32 mm (1¼-inch) pipe, the maximum is 0.9 m; for 38 mm (1½-inch), it is 1.5 m; for 50 mm (2-inch), it is 1.8 m; for 75 mm (3-inch), it is 2.7 m; and for 100 mm (4-inch), it is 3.6 m. Exceeding these limits causes the flowing wastewater to create a siphon effect, drawing water out of the trap and leaving it without a seal.
Question 6: According to the NPCP, what minimum size vent pipe is required for a water closet?
- 25 mm (1 inch)
- 32 mm (1¼ inches)
- 38 mm (1½ inches)
- 50 mm (2 inches) (Correct answer)
Correct answer: 50 mm (2 inches)
A water closet requires a minimum 50 mm (2-inch) individual vent pipe under the NPCP.
The National Plumbing Code of the Philippines Table 9-1 specifies minimum vent pipe sizes based on fixture type. Water closets require a minimum 50 mm (2-inch) vent because of their high drainage fixture unit load (3–4 DFU) and the large volume of water discharged per flush. The vent must be sized to admit enough air to prevent pressure differentials that would siphon the trap. Smaller fixtures like lavatories (25 mm minimum) and floor drains (32 mm minimum) require smaller vents. The vent pipe also must not be smaller than one-half the diameter of the drain it serves.
Question 7: What is the minimum number of water closets required per 100 male employees in a factory or industrial establishment under the Philippine Sanitation Code?
- 1
- 2 (Correct answer)
- 3
- 4
Correct answer: 2
The Philippine Sanitation Code requires a minimum of 2 water closets per 100 male employees in factories and industrial establishments.
Presidential Decree No. 856 and the Implementing Rules and Regulations of the Sanitation Code establish minimum sanitary fixture ratios for various occupancy types. For factories and industrial plants, the requirement is 1 water closet per 1–15 males, 2 per 16–35 males, 3 per 36–55 males, 4 per 56–80 males, and 5 per 81–110 males. For female employees, the ratio is more generous. Additionally, the code requires separate toilet facilities for male and female workers when the workforce exceeds a certain number, and adequate urinals and lavatories must supplement the water closets. These ratios ensure adequate sanitation facilities to protect worker health.
Master Plumber Exam Philippines Master Plumber Code and Regulations 1
Under the National Plumbing Code of the Philippines (NPCP), what is the minimum trap seal depth required for fixture traps?