Drainage Pipe Slope Requirements

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Questions and Answers

What is the minimum slope required for horizontal drainage pipes?

2% (correct)

1.5%

Which type of trap is specifically designed for extreme conditions due to its greater resealing quality?

Drum Trap

Stand Trap

Common P-Trap

Deep Seal P-Trap (correct)

Which fixture unit corresponds to a flow rate of 0.50 to 0.95 L/s?

2 (correct)

What type of trap is used for fixtures built low to the ground that require little space?

Stand Trap Signup and view all the answers

Which of the following traps is prohibited due to its design?

S-Trap Signup and view all the answers

What material is NOT commonly used for P-traps?

Aluminum Signup and view all the answers

For which type of fixture would a drum trap typically be used?

Floor drains Signup and view all the answers

Which of the following statements is true regarding trapping requirements for plumbing fixtures?

Each plumbing fixture, except those with integral traps, shall have an approved-type waterseal trap. Signup and view all the answers

What is the minimum diameter for an individual vent pipe?

32 mm (1-1/4") Signup and view all the answers

What is the minimum distance above the highest fixture level rim that a vent must rise before offsetting?

152 mm Signup and view all the answers

How should horizontal or branch vents be connected to the drainage pipe?

By gravity, free from drops or sags. Signup and view all the answers

What is the minimum distance that a vent opening must be from an openable window?

3.00 m Signup and view all the answers

What is the purpose of a 'yoke vent' in a vent stack system?

To serve as a relief vent. Signup and view all the answers

How far must a vertical vent pipe extend from any part of the roof used for human activities?

3.00 m Signup and view all the answers

What is a cesspool designed to do?

Receive and retain organic matter while allowing liquid to seep through. Signup and view all the answers

When connecting vent stacks to a soil or waste stack, what size should the vent stack be increased to at the connection?

One size larger than the existing pipe. Signup and view all the answers

What conditions must be met for a temporary permit for sewage disposal?

Soil and groundwater conditions must be favorable. Signup and view all the answers

What is the minimum distance a vent termination must be from any vertical surface nearby?

300 mm Signup and view all the answers

What characterizes an outside privy?

Constructed of concrete for collection with a wooden shelter. Signup and view all the answers

What is the purpose of installing an interceptor in a sewage disposal system?

To separate harmful substances such as grease and flammable wastes. Signup and view all the answers

When is a vented leg fitting required in a sewage outlet?

To ensure the outlet is at least 304.8 mm below the inlet fitting. Signup and view all the answers

What is the minimum liquid capacity requirement for the first compartment of a septic tank?

2 cubic meters Signup and view all the answers

What is the maximum capacity for the secondary compartment of a septic tank?

1/3 of the total tank capacity Signup and view all the answers

How should the bottom of the digestion chamber be sloped for sludge collection?

1:10 Signup and view all the answers

What is the minimum dimension for manholes in a septic system?

508 mm Signup and view all the answers

What is the minimum diameter for the vertical legs of inlet and outlet pipes?

104.6 mm Signup and view all the answers

What must the invert of the inlet pipe be above the invert of the outlet pipe?

50.8 mm Signup and view all the answers

What type of material is most commonly used for constructing septic tanks?

Cement Signup and view all the answers

Which is prohibited for use as a partition between compartments in a septic tank?

Wooden baffles Signup and view all the answers

What is the minimum horizontal distance required between a water pipe and a sewer or drain pipe when placed in a common trench?

0.3 m Signup and view all the answers

What is the minimum required distance from a water supply well to a building sewer?

15.2 m Signup and view all the answers

Which factor determines the area required for a private sewage disposal system?

Soil type and sewage flow rate Signup and view all the answers

What is the minimum required excavation distance from the water table for leach beds?

1.5 m Signup and view all the answers

What is the required compressive strength of the brick lining in a seepage pit?

17225 kPa Signup and view all the answers

When placing a water pipe above a sewer or drain pipe, what is the minimum vertical distance that should be maintained?

0.3 m Signup and view all the answers

What is the minimum diameter that a circular seepage pit must have?

2.2 m Signup and view all the answers

How far must a water pipe joint be installed from the sewer line in both directions?

3 m Signup and view all the answers

What is the minimum required distance from buildings to a septic tank?

2.4 m Signup and view all the answers

Which of the following is NOT a feature of a Sewage Treatment Plant (STP)?

Water filtration bed Signup and view all the answers

What is the distance required from water supply wells to cesspools?

45.7 m Signup and view all the answers

In the Activated Sludge Process, what is the purpose of the grit chamber?

To remove heavy materials Signup and view all the answers

How far must a disposal field be from the property line?

1.5 m Signup and view all the answers

What is the overall purity of the water produced through the Activated Sludge Process?

99-99.5% Signup and view all the answers

What is the minimum distance required from trees to a septic tank?

3 m Signup and view all the answers

What process occurs after the second phase in the Activated Sludge Process?

Hardening of the sludge Signup and view all the answers

Study Notes

Plumbing Systems Overview

Components of a plumbing system include: water distribution system, fire protection system, plumbing fixtures, sanitary drainage system, storm drainage system, and fuel gas piping system.

Sanitary Drainage System

Piping should be routed to the shortest point to the house sewer.
Control components (clean-outs, traps, vents) should be strategically placed for efficient circulation.
Subsystems include waste collection and ventilation systems.

Essential Parts of the Sanitary Drainage System

Waste Pipe: Carries wastewater without fecal matter.
Vent Pipe: Ensures air circulation in plumbing and relieves negative pressure on trap seals.
Trap: A fitting preventing backflow of foul air or methane gas without affecting sewage flow.
Stack: The main vertical pipe for soil, waste, or vent piping, extending to the roof.
Branch: Any pipe part other than a main, riser, or stack.

Essential Parts of the Sanitary Drainage System (Continued)

House/Building Drain: The lowest horizontal pipe receiving discharges from inside the building and connecting to the house sewer.
House/Building Sewer: Extends from the house drain to the street sewer or discharge points, carrying drainage from one building site. (NPC 203.3)

Changes in Direction of Sanitary Drainage Lines

Horizontal to horizontal: 45° wye branches, combination wye – 1/8 bend branches, or equivalent sweep fittings.
Vertical to horizontal: 45° wye branches or equivalent sweep fittings.
No fitting should have more than one inlet at the same level (i.e., sanitary cross).
Double sanitary tees may be used if the barrel is at least two pipe sizes larger than the largest inlet.

Unit of Measurement of Sanitary Drainage Lines

Pipe sizes depend on the amount of waste carried.
A lavatory discharges 0.47 liters/sec or 28.3 liters/min (7.5 gallons per min or 1 cu ft per min, equivalent to Fixture Unit (F.U.)
F.U. rating of plumbing fixtures is based on trap size.

Maximum Trap Loading

Maximum trap loading varies based on pipe size and fixture unit.
There is an exception for self-service laundries.
Capacity over 3.15 L/s is determined by the Administrative Authority.

Minimum Slope of Sanitary Drainage Lines

Minimum slope of horizontal drainage pipe is 2% or 20mm/m (1/4" per foot).
1% or 10 mm/m (1/8" per foot) slope may be used for pipes of 102mm or larger (with approval).

Types of Permissible Traps

Common P-Trap: Used for lavatories, sinks, tubs, and urinals.
Materials include nickel, chrome-plated brass, galvanized malleable copper, and PVC.
Deep Seal P-Trap: Used for extreme conditions, having a larger water seal than a common P-trap.
Stand Trap: Used for fixtures like slop sinks that are low in the ground, serving as a water seal and structural support.
Drum Trap: Used for fixtures with high water discharge like bathtubs and shower floors; has a large diameter.

Types of Prohibited Traps

Traps with movable Parts or concealed interior partitions are prohibited.
Fixtures should not be double-trapped.
S-traps (predecessors of P-traps) are prohibited.

Traps Required

Each plumbing fixture (excluding those with integral traps) needs a separate water seal trap.
Only one trap per trap arm (portion of a fixture drain between a trap and vent) is allowed.
Up to three single compartment sinks, or tubs, or lavatories in the same room may share one trap if waste outlets are less than 0.75 m apart.

Size of Traps

Trap size must match the trap arm size.
Trap seal water depth must be between 51 mm and 102 mm (unless a deeper seal is needed).

Installation of Traps

The vertical distance from a fixture tailpiece to the trap weir should not exceed 0.60 m (24 inches).
Horizontal trap arm distances vary based on diameter; there is a minimum of two times the diameter of the trap arm.
Developed length of trap arm should not exceed 1.8 m.
Cleanout required for changes of direction > 22 1/2°.

Industrial Interceptors (Clarifiers) & Separators

Interceptors separate and retain unwanted materials from normal waste. They must have a minimum water seal of 152 mm deep.
They should be properly vented.
Slaughterhouses, packing plants, and facilities with significant grease, hair, or feather waste must have screening devices and grease interceptors.
Auto wash areas must have interceptors to separate oil and grease.

Clean-Outs

Clean-outs are required at the end of every horizontal sewer or waste line exceeding 15 meters. Additional clean-outs are required every 15 meters (or fraction thereof) in lines with offset angles exceeding 135°. Clean-outs also positioned at the lower end and extended to grade.
Clean-outs not required on short horizontal drains less than 1.5 m, and or lines with a slope of 72 degrees or less.

Clean-Outs Size

Clean-outs' size must match the served pipe size.
Specific sizes and threads are included for different pipe sizes.

Installation of Clean-Outs

Clean-outs should open in line with flow, or at a 90° angle; exceptions apply to wye branches
90° clean-outs should be constructed from a wye fitting, or an approved equivalent
Clearance from 51 mm or less clean-outs = 305 mm, while more than 51 mm clean-outs = 450 mm.

Ventilation

Ventilation ensures balanced atmospheric pressure and negative pressure relief on trap seals.
Provides proper air circulation within the plumbing system.

Main Types: Main Soil & Waste Vent

Main Soil & Waste Vent serves as the backbone of the sanitary system.
It connects to the main soil and waste stack.
Waste not passing all the way through to the roof is called the Vent Stack Through Roof (VSTR).

Main Vent

Main vent is the principle artery of the venting system, and all vent branches are connected to it.
Also known as the Collecting Vent Line.
Supports the Main Soil and Waste Vent.

Individual Vent or Back Vent

Installed to vent a fixture trap and connects with the vent system or terminates in the open air above the fixture.

Unit, Common, or Dual Vent

An arrangement of installing one vent pipe serving two traps.

Relief Vent

A vertical vent line for additional air circulation between the drainage and vent systems; acts as an auxiliary vent such as a "yoke vent", connecting soil and vent stacks

Yoke or By-pass Vent

Connects vertically upwards from a soil or waste stack that is below a floor to an adjacent vent stack, above the floor, and higher than the highest fixture spill level.
This prevents pressure changes in the stack.

Circuit Vent

A group vent line originating from the highest extreme fixture connection to the vent stack on the horizontal branch.
Also known as a Loop Vent.
Serves a battery of fixtures.

Looped Vent

A vertical vent connection branched off a horizontal soil or waste pipe, located downstream of the last fixture connection.
It extends horizontally above the highest highest level of the fixture for overflow prevention.

Wet Vent

A vent pipe through which wastewater flows.

Local Vent

A pipe or shaft that conveys foul air from plumbing fixtures to the outer air.

Dry Vent

A vent that does not carry water-borne wastes.

Stack Vent

Extends a soil or waste stack above the highest horizontal drain connected to the stack.

Vent Stack

The vertical vent pipe installed for providing air circulation to and from parts of the drainage system; its uppermost end is referred to as Vent Stack Through Roof (VSTR).

Vents Required

Each trap must be protected against siphonage and back-pressure by venting.

Vents Not Required

Vents aren't required on primary settling tank interceptors if they discharge indirectly into properly trapped and vented secondary interceptors.
In island bar counter sinks, sinks discharge through approved indirect pipes to another floor sink or other suitable receptor.

Size of Vents

Vent pipe sizes should be determined based on length and number of fixture units connected to it.
Vent diameter must be at least 32 mm or half the drain diameter, whichever is larger.

Installation of Vents

All horizontal or branch vents should be free of dips or sags.
Vents shall rise vertically 152 mm above the highest rim of the fixtures served before offsetting horizontally.
All vent pipes must extend undiminished above the roof, or be reconnected to the soil or waste stack vent below the roof;
Increase in vent size occurs at the horizontal vent connection to the vent stack.
Two fixtures at the same elevation may share a vent using a double branch fitting.

Vent Termination

VSTRs should be 150 mm above the roof or 300 mm from any vertical surface near the nearby area.
Vent must be 3 m from any openable window, 0.9 m above openable windows, and at least 0.9 m from lot lines, alleys, and street boundary lines.
Vertical vent should be at least 2.10 m above the roof.

Installation of Vent Stacks & Relief Vents

Soil and waste stacks with ten or more stories require parallel vent stacks connecting to them and extending to the soil or waste stack at ground level and at the fifth floor levels
Vents should be connected with a yoke vent for relief.
Yoke vent diameter is as large as the smaller diameter between the vent stack and soil stack.
Yoke vent should be 1 m above the floor level.

Sanitary System Problems: Trap Seal Loss

Direct effect of minus and plus pressure inside the system due to inadequate ventilation of traps.
(Attributed to siphonage, direct and momentum)

Sanitary System Problems: Back Pressure, Capillary Attraction and more

Back pressure, capillary attraction, evaporation, wind effect, retardation of flow, and material deterioration can cause trap seal loss.
Capillary attraction is due to adhesion and cohesion in fluids.
Causes include extreme temperatures, idleness, winds, and gravity.
Material deterioration is often due to acid formation.

Indirect Waste Pipe

Pipes that do not connect directly to the drainage; instead, they discharge into a plumbing fixture, interceptor, or receptacle connected to the drainage.

House Drain Appliances: Grease Traps

Required for establishments with potentially high grease production (restaurants, etc.), but not for individual dwellings.
Grease traps with approved water seals (at least 51mm deep or the outlet diameter).
No food waste disposal is connected directly to grease traps or their interceptors

Grease Traps 2 Main Types

Earth-Cooled and Mechanical

Operating Principles of Grease Traps

Grease suspends in waste, floats to the surface and is separated.

House Traps

Placed inside the house drain immediately inside the foundation wall of the building.

Drain Tiles

Used to prevent groundwater from seeping through basement walls and foundation.
Hollow tiles are placed around the perimeter and are connected to the house drain or sump pit.

Garage Traps

Alternative name for garage catch basins, which collect all garage wastes at the lowest point.

Back Flow Valves

Used to prevent backflow in the house drain.
Similar to check valves.

Sewage Ejectors

Pumps to transfer waste from the sump pit to sewers, which are usually at higher levels than the basement.

Private Sewage Disposal Systems: Definition and more

Watertight receptacle for receiving sewage, separating solids from the liquid, digesting organic matter and allowing the clarified liquids to discharge for final disposal
Sludge is solid organic matter which is denser than the water and settles at the bottom of the tank; scums are organic materials in the septic tank that rise to the surface of the water.
Effluent is the liquid waste.

Private Sewage Disposal Systems: Bacteria

Aerobic bacteria rely on oxygen to survive.
Anaerobic bacteria survive in oxygen-free environments.

Private Sewage Disposal Systems: Minimum Dimensions

Minimum dimensions for septic tanks: Length= 1500mm; Width= 900mm; Depth=1200mm.

Private Sewage Disposal Systems: Single Chamber Septic Tank

A single compartment tank for holding waste, with inlet and outlet tees for sewage flow.

Private Sewage Disposal Systems: Design Criteria

Plans must show dimensions, reinforcing, and calculations. -Design must produce clarified effluent of acceptable standards and sufficient space for sludge and scum.
Materials must be durable, resistant to corrosion or decay and watertight; (cement or pre-fabricated cast iron most often used)

Private Sewage Disposal Systems: Compartments

-Minimum 2 Compartments are required, First compartment (not less than 2/3 the capacity), and Second compartment (minimum 1/3 total capacity)

For septic tanks over a capacity of 6 cum the secondary compartment needs to be 1.5 m in length. -The bottom of the digestive chamber needs to have a 1:10 slope for the proper collecting of sludge.

Private Sewage Disposal Systems Pipe Inlets and Outlets

Inlet and outlet pipes must have a diameter equal to or bigger than the sewer pipe.
Vertical legs for inlets and outlets must be a minimum of 104.6 mm in diameter.
Inverted pipe must extend at least 101.6 mm above and at least 304.8 mm below the water’s surface.
Invert of the inlet pipe should be at least 50.8 mm above the invert of the outlet pipe.
Vent diameter should equal the cross-sectional area of the house sewer.

Private Sewage Disposal Systems: Air Space

-Sides of the sidewalls should extend 228.6mm above the liquid depth. -The cover to the septic tank should be at least 50.8 mm above the openings to the back vent.

Private Sewage Disposal Systems: Partitions

Partitions made of inverted fittings and should have a size of 104.6mm, with the bottom of the fitting in the middle of the liquid depth. Wooden baffles are prohibited.

Private Sewage Disposal Systems: Structure

Structure must be capable of handling the earth load of at least 14.4kPa,

Private Sewage Disposal Systems Capacity

Capacity depends on the number of bedrooms or units in a given occupancy or number of fixtures; whichever is the greatest. -Capacity is also limited by the structure of the soil classification in the sewage disposal area.

Private Sewage Disposal Systems: Location

Septic tanks or systems should be located away from the water distribution system, a distance of 15 meters.

Sewers: 3 Degrees or Grades of Waste Water

Grey water (area water): Waste water from laundries, wash basins, sinks, tubs.
Black water: Waste water including solids and liquids from humans.
Storm Water: Rainwater only

Sewers: Classification of Sewers

Combination Public Sewers: Carry both storm and sanitary wastes (oldest type).
Storm Sewers : Carry only rainwater.
Sanitary Sewers : Carry only domestic waste water and is designed to ultimately flow to a sewage treatment plant.
Built at a depth of 3 meters below the ground surface (for tributaries).

Sewers: 2 Types of Sanitary Sewers

Tributary Sewers: Individual units connection points, usually round shaped between 0.60 m to 1.2 m in diameter, made of vitrified clay or cement pipes.
Intercepting Sewers: Placed at lower levels in the ground (4–30 Meters) as termination points of tributary sewers and varying in shape, but typically have an effective opening from 0.60 to 3 meters.

Sewers: Requirements

Drainage pipes for all buildings are connected to public sewers.
No connections to public sewers are allowed if located more than 61 m from the building or facility.
Private sewage disposal systems can be substituted for public sewers when there are no hazards, nuisances, or unsanitary conditions present and sufficient grading and fall exist for all drainage to flow by gravity.

Sewers: Damage to Public or Private Sewage Disposal

It’s unlawful to discharge ashes, cinders, solids, flammable materials, poisonous, explosive liquids, or gases, oils, grease, or other harmful materials into the public or private sewage disposal system
Rain or surface (or subsurface) water should not enter into any excreta drainage system.
Cesspools and septic tanks and their discharge should not be connected to a public sewer main.
Commercial food waste grinders may not be connected to public or private sewage disposal systems

Sewers: Size of Sewer

Minimum size of a building sewer shall be based on the total of fixture units drained; no sewer can be smaller than the building drain. The minimum diameter of 150 mm is mandated.

Sewers: Installation of Sewer

Building sewers should be in alignment and slope at least at 2% or 21 mm/m towards the disposal point; an exception exists for impractical locations regarding depth of street sewers, structural features, or adverse arrangements.
In such impractical cases, pipes 102 mm to 152 mm in diameter may have a slope of at least 1% or 10.5 mm/m, and those with 203 mm or larger may have a slope of at least 0.5% or 5.3 mm/m.

Sewers: Location of Sewer

No building sewer should be situated closer than 0.6m from the face of the building nor less than 30cm below the ground’s surface.
Placement of sewer pipes must maintain a 0.6m distance from buildings or structures
A distance minimum of 15.2 meters from the water supply wells should be maintained.
A distance minimum of 0.30 meters from domestic water pipes and a distance of 0.30 meters from public pipes should be maintained.
Pipe installations should be placed in different trenches from water pipes, if necessary, at minimum of 0.3 m from the top of the sewer.

Water/Sewage Pipes Crossing

Water pipes crossing sewer or drainage pipes must have a minimum of 0.3m clearance above the sewer pipe.
Water pipe joints should be 3 m away from the sewer line on either side.

Disposal Fields

Sewage disposal systems that utilize open fields for drainage in rural areas.

Disposal Fields: Area, Distance from water table, With seepage pit

Area dependent is based on required septic tank capacity or estimated sewage flow rate.
Excavations for leach beds shall not be within 1.5 m of the water table. -Filter material in the trenches shall terminate 1.5 m from the pit excavation, with the pipe extending to the pit being watertight.

Sewage Pits: Capacity, Size, Strength Multipe Sewage Pits

Capacity based on the quantity of liquid waste and surrounding soil's porosity and character.
Circular shape with an excavated diameter of at least 2.2 m, lined with clay or concrete brick.
Brick lining should have a compressive strength of at least 17225 kPa.
Multiple sewage pits may be connected through distribution boxes and watertight connections; with a vented leg extending at least 304.8 mm below the inlet fitting.

Cesspools

Non-watertight excavations receiving waste from a drainage system designed to retain solids but allow liquids to seep through the bottom and sides.

Temporary Permits

Temporary permissions for sewage disposal options while waiting for the construction of a public sewer or when conditions are favorable.
Can serve as overflow facilities, or for temporary limited use.

Privies

Outside Privies are the oldest method of sewage disposal, consisting of a concrete vault for collecting raw sewage with a wooden shelter.

Commercial/Industrial Special Liquid Waste Disposal: Requirements and Disposal

For liquid wastes containing excessive amounts of grease, garbage, flammable waste, sand or other ingredients which can affect a private sewage disposal, an interceptor should be installed.
Waste from interceptors must be discharged to septic tanks or other primary systems; or a separate disposal system.

General Guidelines for Private Sewage Disposal Systems: Location

Minimum horizontal distances, measured in clear from buildings or structures, property lines, water wells, streams, trees, cesspools, or drainage fields, sewage pits, domestic water service lines, and public water mains to the septic tanks and related components are provided in a table.

Sewage Treatment Plan (STP): Features

Aeration systems, submersible mixers, sludge pumps to clarify, decanters and blowers for handling the waste and a fully electronic control system are features of an STP.

2 Most Common Municipal Sewage Treatment Types (The Activated Sludge Process)

Involves a series of stages (first, second, and third phases), utilizes multiple filter houses and clarifiers to remove heavy materials, clarify effluent, convert sludge into fertilizers and achieve high levels of purity (99.95%).

2 Most Common Municipal Sewage Treatment Types (The Trickling Filter Process)

Relies on mechanical elements for less phases.
Produces water with 95% purity, but requires large ground areas for its treatment.

Storm Drainage System

A system for collecting rainwater for proper drainage that will not be used for other purposes.

Rainwater Pipes, Downspouts or Conductor Pipes, Gutters - more details

Rainwater piping should not be used for soil, waste, or vent piping.
Down spout and gutter sizes are based on the maximum rainfall depth in rainfall per hr., and the area of the roof covering.
A rainfall intensity of 102 mm/hr is commonly used in Metro Manila.
Round, square or rectangular pipe can be used, but the cross-sectional area cannot be less than that of a round pipe;
Sides of a rectangular pipe should have a ratio of 3 to 1

Rainwater Pipes, Roof Drains - more details

Roof drains must have dome-type strainers extending 102 mm above the roof surface, with a minimum net area of 1 - 1 1/2 times the area of the outlet pipe.
Roof deck strainers must be flat surface type with minimum net area of double the outlet pipe area.
Roof drains within the building must be made watertight with a cast waterstop ring placed at mid-depth of the concrete slab, with suitable flashing material around the drain itself.

Storm Water Systems: The Independent (Separate) System

A separate system which brings collected water directly to the water reservoirs

Storm Water Systems: The Combined System

Storm water from the building roof and the roadways from above are combined with sanitary wastes.

Storm Water Systems: The Natural System

Natural rainwater collection systems without downspouts or gutters.

Storm Water Systems: Roofing Elements

Gutters
Downspouts
Strainers
Roof Drains
Shoes (direct water flow to nearest catch basin)
Catch basins
Storm lines

Storm Sewers

Carry rainwater only, terminating at natural drainage areas such as lakes, rivers, or water reservoirs
Sewers should require manholes to allow inspection and repairs

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This quiz explores the essential guidelines for the minimum slope required for horizontal drainage pipes. Understanding these requirements is crucial for ensuring proper drainage and preventing water accumulation. Test your knowledge about drainage systems and their specifications!