BUILDING PLUMBING SYSTEM (Part-2)
Definition of Plumbing
The plumbing includes the practice, materials, and fixtures used in the installation., maintenance,
extension, and alteration of all piping, fixtures, appliances, and accessories in connection with sanitary
drainage or storm drainage facilities, the venting system and the public or private water supply
systems/within or adjacent to any building, structure, or conveyance.
Major elements in plumbing systems
The plumbing system includes
 water supply and distribution pipes : riser, up feed or down feed distribution pipes , UGWR, OH
tank
 plumbing fixtures and traps,
 soil, waste and vent pipes,
 building drains and building sewers, including-their respective connections, devices, and
appurtenances within the property lines of the premises
Some Important Terminologies
Plumbing Fixture:
 The water-supply system of a building distributes water to plumbing fixtures at points of use.
 Fixtures include kitchen sinks, water closets, urinals, bathtubs, showers, lavatories, drinking
fountains, laundry trays, and slop (service) sinks.
 The plumbing fixtures are at the terminals of the water-supply system and the start of the
wastewater system.
 Each fixture is served by a soil stack, or waste stack, a vent or vent stack, and a trap
Fixture unit:
is the average discharge, during use, of an arbitrarily selected fixture, such as a lavatory or water
closet. Once this value is established, the discharge rates of other types of fixtures are stated in terms
of the basic fixture.
Riser :
A water supply pipe which extends vertically one full storey or more to convey water to branches or
fixtures or to OH tank
Waste Pipe :
A waste pipe is a pipe which conveys only liquid waste free of faecal matter
Soil Pipe :
A soil pipe is any pipe which conveys the discharge of water closets, urinals, or fixtures having similar
functions, with or without the discharge from other fixtures, to the building drain or building sewer.
Vent Pipe :
A vent system is a pipe or pipes installed to provide a flow of air to or from a drainage system or to
provide a circulation of air within such system to protect trap seals from siphonage and back pressure.
Stack:
A stack is the vertical main of a system of soil, waste, or vent piping.
1
Stack Vent/Soil Vent:
A stack vent (sometimes called a waste vent or soil vent) is the extension of soil or waste stack above
the highest horizontal drain connected to the stack.
Vent Stack:
A vent stack is a vertical vent pipe installed primarily for the purpose of providing circulation of air to
and from any part of the drainage system.
2
Trap:
A trap is a fitting or device so designed and constructed as to
provide, when properly vented, a liquid seal which will prevent the
back passage of air without materially affecting the flow of
sewage or waste water through it.
Trap seal:
The trap seal is the maximum vertical depth of liquid that a trap
will retain, measured between the crowrn weir and the top of the
dip of the trap.
Clean-outs(CO):
A clean-out is an opening that provides access to a pipe, either directly or through a short branch, to
permit cleaning of the pipe. The opening is kept plugged, until the plug has to be removed for cleaning
of the sewer. In horizontal drainage lines, at least one clean-out is required for each 100 ft of pipe.
Water Distribution in a Building
Water distribution in to building can be done in many way:
1. Upfeed distribution
Simple upfeed :
– Water fed to fixtures in a building only by the incoming pressure of the supply water.
– This method is good for buildings up to 5 to 6 stories high.
Pumped upfeed
– Water fed to the fixtures in a building by increasing the pressure of the supply water using
additional pumps.
2. Down Feed Distribution
– Uses pumps to deliver water to a rooftop storage tank of the building.
– The water in the storage tank feeds fixtures below due to the force of gravity.
– Commonly one roof top tank is used to distribute water to whole building. For tall building
intermediate tank(s) are often used to supply water at different levels.
– If main does not have sufficient pressure to carry water to OH tank, underground water reservoir
(UGWR) is provided to store water from main and deliver to the overhead tank
Design of Down Feed Water Supply System
Design Components:
1. Sizing of Water Distribution Pipes within the Building
2. Dimensions of UGWR
3. Dimensions of OH tank
4. Determination of size of riser
5. Calculation of Pump capacity
Details of this calculation is given in the previously supplied handout.
3
4
Basic Elements of Drainage System
1. Drainage pipes
• Soil pipes
• Waste pipes
• Vertical pipes are known as stacks (soil / waste / vent)
2. Traps
• Placement
• Depth of trap seal
• Cleaning
3. Vents
• Purpose - ventilate plumbing system&revent foul gases from drainage system to enter the
building
• Vent stack size
Pipes and fitting materials
– cast iron
– copper
– plastic [acrylontile butadiene styrene (ABS)
– polyvinyl chloride (PVC)
– styrene rubber plastic (SRP)]
Change of direction- no right angle connection; use 45° Y, combination of Y and 1/8” bend or long
sweep
Cleanouts -Removal of obstructions
•
Factors Affecting Size of a Horizontal Branch Drain
– Connected DFU to the branch drain
– Size of the largest individual drain connected to the branch
•
Factors Affecting Grade or Slope of a Drain pipe
– Size of branch drain
– Connected DFU to the branch drain
•
Factors Affecting Vent Pipe Size
– Size of largest drain pipe connected to the vent pipe
– Connected DFU
– Developed length of the vent pipe
5
Design Steps
1. Provide individual soil pipe, waste pipe and vent pipe for each bathroom on each floor
2. Provide one waste pipe and vent pipe for kitchen on each floor
3. Calculate total DFU (drainage fixture units) using table 14.4 for all fixtures connected to each soil
pipe waste pipe.
4. Determine trap size using same table
5. Using Table-14.13 determine the size of soil and waste pipe. e.g., use 3rd column of the table for
total DFU of multistoried building.
6. Using table-14.12 determine the size for vent pipe
7. Draw and show the details of drainage system
Other requirements:
– A water closet must have a 2 inch vent
– Individual vents from any other fixture shall not be less than 1 1/4 inches
– Connections of pipes should be at 45 ° angles
– Cleanouts should be provided every 50 ft of horizontal length
– Cleanouts also should be provided at all stack bottoms
– Vent stack height should continue at least 5 ft above top roof
Following sizes of drainage pipes are commonly employed
Soil pipe
100 mm
Waste pipe, horizontal
32 mm to 50 mm
Waste pipe, vertical
75 mm
Vent pipe
50 mm
6
7
8
9
10