Drainage System Overview

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Questions and Answers

What is the primary function of the house trap in a plumbing system?

To prevent sewer gases from entering the building (correct)

To filter out harmful substances

To increase water pressure in the system

To retain solid waste temporarily

What defines the size of waste pipes or soil pipes in a sanitary drainage system?

The materials used for construction

The types of fixtures used

The amount of waste it carries (correct)

The length of the pipe

A lavatory discharges 0.47 liter/sec. How many fixture units (F.U.) does it equate to?

3 F.U.

0.5 F.U.

1 F.U. (correct)

2 F.U.

What is the design purpose of a septic tank?

To retain solid organic matter Signup and view all the answers

Which of the following is an example of a permissible trap used in plumbing systems?

Common P-Trap Signup and view all the answers

Which part of the plumbing system is responsible for conveying discharges to the house sewer?

House/building drain Signup and view all the answers

What component of a sanitary drainage system retains organic matter?

Septic tank Signup and view all the answers

What does a private sewage disposal system comprise primarily of?

A septic tank Signup and view all the answers

What does the drainage system not include?

The mains of a public sewer system Signup and view all the answers

Which subsystem is responsible for conveying fecal matter?

Soil drainage system Signup and view all the answers

What is the primary function of the vent system in drainage systems?

To circulate air and protect trap seals Signup and view all the answers

Which component extends from the house drain to the street sewer?

House/building sewer Signup and view all the answers

Which type of drainage system specifically excludes sanitary wastes?

Storm drainage system Signup and view all the answers

What does the term 'stack' refer to in a drainage system?

The vertical main of a soil or waste system Signup and view all the answers

What is the main purpose of a trap in a drainage system?

To prevent the backflow of foul air or gases Signup and view all the answers

Which statement about the waste drainage system is true?

It is free of fecal flow Signup and view all the answers

Which material is NOT commonly used for P-traps?

Stainless steel Signup and view all the answers

What is the purpose of the Stand Trap?

To serve as structural support for low fixtures Signup and view all the answers

What is a significant issue with using S Traps?

They can siphon water out and release sewer gases Signup and view all the answers

What failure mode is associated with Bell Traps?

Vulnerability to drying out Signup and view all the answers

What additional feature does a Crown Vented Trap have compared to a standard S Trap?

An air vent connected at the crown Signup and view all the answers

Which of the following traps is specifically designed to handle large amounts of water?

Drum Trap Signup and view all the answers

What is a critical requirement for traps in plumbing systems?

A cleanout and relieving vent must be provided Signup and view all the answers

What is the minimum slope required for horizontal drainage pipes?

20mm/m or 2% Signup and view all the answers

What slope is allowed for pipes of 102mm or larger if impracticable to obtain the standard slope?

10mm/m Signup and view all the answers

What angle must be used to change the direction of drainage flow using a bend?

22 1/2 degrees Signup and view all the answers

Which fitting is NOT used for changing drainage flow from Horizontal to Vertical?

Rubber couplings Signup and view all the answers

When piping passes under or through walls, what protective measure is recommended?

Metal pipe sleeves Signup and view all the answers

What is the minimum angle required for the bottom of pipe trenches deeper than the footing of adjacent structures?

45 degrees Signup and view all the answers

What type of support is required for Bell & Spigot & Hubless pipe in vertical piping?

At every storey or closer Signup and view all the answers

Which combination of fittings is used for drainage flow changes from Horizontal to Horizontal?

Combination of 45-degree & 1/8 bend Signup and view all the answers

When is it impracticable to obtain the standard slope in drainage piping?

Due to structural features of the terrain Signup and view all the answers

Study Notes

Drainage System

The complete drainage system is subdivided into four subsystems: Soil drainage, Waste drainage, Vent system, and Storm drainage system.
The Soil drainage system conveys the discharge of water closets or fixtures containing fecal matter, with or without the discharges from other fixtures.
The Waste drainage system receives the liquid discharge from plumbing fixtures other than those fixtures (water closets) receiving fecal matter, it has no fecal flow.
The Vent system receives flow or air to or from a drainage system or to provide circulation of air within the drainage system to protect trap seals.
The Storm drainage system receives clear water drainage from leaders, downspouts, surface run-off and conveys them to the point of disposal.
Sanitary wastes must be excluded from the Storm drainage system.

Sanitary Drainage System Components

A trap is a fitting or device designed to provide a liquid seal which prevents the backflow of foul air or methane gas without affecting the flow of sewage or waste water through it.
A branch is any part of the piping system other than a main, riser or stack.
A stack is the vertical main of a system of soil, waste or vent piping extending through one or more stories.
The house/building sewer extends from the house drain at a point 0.60m from the outside face of the foundation wall of a building to the junction with the street sewer or to any point of discharge, conveying the drainage of one building site.
The house/building drain is the lowest horizontal piping of a plumbing system that receives discharges from the soil, waste and other drainage pipes inside a building and conveys it to the house sewer outside.
The house trap/building trap is a device installed in the house drain immediately inside the foundation wall of the building. It serves as a barrier and prevents gases from the public sewer or septic tank from circulating through the plumbing system.
A septic tank is a watertight receptacle that receives the discharge of a drainage system and is designed to retain solid, digest organic matter through a period of detention.
A private sewage disposal system uses a septic tank with the effluent discharging into a subsurface disposal field, seepage pits or other facilities permitted by the plumbing code.

Sanitary Drainage System Unit of Measurement

The size of waste pipes or soil pipes depends on the amount of waste it carries.
A lavatory discharges 0.47 liter/sec or 28.3 liters/min (7.48 gallons per min or 1 cu ft per min), which is equivalent to one Fixture Unit (F.U.)

Traps

The common P-trap is used for lavatories, kitchen sinks, laundry tubs, & urinals, it is made of nickel, chrome plated brass, Galvanized malleable copper, & PVC.
The Deep Seal P-trap has a water seal about twice the size of the common P-trap, used for extreme conditions because resealing quality is greater.
The Stand Trap is used for fixtures such as slop sinks, it serves as a water seal & structural support for the fixture.

Prohibited Types of Traps

The S trap is a predecessor of P-traps, it can easily siphon water out of the trap which will release methane (sewer) gases into the home.
The Bell trap is designed to be used in garages, balconies or anywhere else outside. It can fail due to its vulnerability to drying out and accumulating decaying, organic debris.
The Crown Vented Trap is an S-trap with an air vent connected at or near the uppermost crown of the S. Heavy flow down the drain could briefly backup into the crown, debris could collect there and clog the vent.

Trap Types for Special Conditions

The Running Trap is used within the line of the house drain. It is a "U"-shaped trap.
The Drum Trap has a large diameter (around 0.16 m), used for fixtures that discharge large volumes of water (bathtubs, showers or floor drains).

Trap General Considerations

No fixture shall be double-trapped.
No trap shall be installed without a vent.
A building trap shall not be installed except where required by the authority having jurisdiction.
Each building trap, when installed, shall be provided with a cleanout and with a relieving vent or fresh-air intake on the inlet side of the trap.

Grade of Horizontal Piping

Drainage pipes shall be run at a minimum slope of 20mm/m or 2% toward the point of disposal.
Pipes 102mm or larger in diameter may have a slope of 10mm/m or 1% provided it is approved by the administrative authority.

Changes in Direction of Drainage Flow

Changes in direction of piping shall be made using approved fittings.
Permitted fittings include: 22 1/2 degrees bend (1/16) bend, 45 degrees bend (1/8) bend, 60 degrees bend (176) bend or other approved fittings of longer sweeps.

Horizontal to Vertical

45-degree wye branches
60-degree wye branches
Combination of-45 degree & 1/8 bend branched
Sanitary Tee
Double Sanitary Tee

Horizontal to Horizontal

45-degree wye branches
Combination of-45 degree & 1/8 bend branched
Or other approved fittings of equivalent sweep

Vertical to Horizontal

45-degree wye branches
Combination of-45 degree & 1/8 bend branched
Or other approved fittings of longer sweep
60-degree branches or offsets (only for pipes installed in true vertical position)

Protection of Pipe Materials and Structures

The bottom of all pipe trenches deeper than the footing of any adjacent building or structure & parallel to it must be at least 45 degrees.
All pipings passing under or through walls shall be protected from breakage with embedded metal pipe sleeves.
Voids between pipes & sleeves through concrete floors in the ground shall be sealed with bitumen.

Hangers and Supports

Cast Iron Soil Pipe - Bell & Spigot & Hubless pipe shall be supported at every storey or closer.

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Description

This quiz covers the essential components of drainage systems, including soil drainage, waste drainage, vent systems, and storm drainage. Each subsystem's functions and importance in sanitation and water management will be examined. Test your knowledge on how these systems operate and their roles in effective drainage management.