SERVICES IN HIGH RISE BUILDINGS
YAR104
UNIT –II -1
WATER SUPPLY
Ar. N.Ramesh Babu. B.Arch,M.T.P
Associate Professor
Department of Architecture
Periyar Maniammai Institute of Science
and Technology
Challenges in Servicing High-rise Water Distribution
• Pressure management – Plumbing
• Supplying adequate water pressure at all levels of the building
(PRV, Boosters)
• Design challenges in complex high rise structures.
• Impact of piping systems on the general construction of the
Building.
• Uniqueness in form and specific design solutions.
• Requires close scrutiny and evaluation to maximize
the project’s potential for the owner and to create a design that is
robust enough to serve the needs of the building for years
Understanding Pressure
Water has the unfortunate quality of being heavier than air.
one psi will lift water 2.31 feet (1/0.433).
• high water pressure not to exceed 80 psi.
• 70 psi will result in more manageable flow rates at the fixtures,
reduced water hammer and lower velocities.
• Low water pressure upto 20 psi, unless there are fixtures such
as flush valves that require greater pressures.
• A minimum pressure of 40 psi is recommended for the comfort.
• With a pressure differential of 30 psi, a zone can be no more
than 69 feet in height (30 ft x2.31 ft/psi). Using a typical floor to
floor height, for a hotel, of 11 feet, no more than six floors can be
served by a single zone.
Cold water supply system
• Cistern Feed (indirect) – supply comes from independent of the
main from a cistern.
• Direct Feed (direct) - supply comes directly from the main.
Hot water supply system
• Central system– water is heated and stored centrally.
• Local system– water is heated and stored locally
Types of Water distribution in High-rise buildings
• Main pressure supply
• Pumped and Main pressure supply
• Multiple risers
• Gravity feed cold water supply
• Low level storage cistern
• Intermediate level storage cistern
1 Main pressure supply
• Supplied under pressure from head of water from a reservoir,
or pumped head of water.
• Main pressure will rise less in a building on high ground.
• Pressure will be at an increased level in a building on low
ground.
• Reduced pressure during peak hours.
• Determination of pressure during peak hours will be
appropriate.
Pressure depends on
• Natural/ artificial pressure available
• Intensity of demand on the main during Peak hours.
• Relative level of building to the supply pressure.
Main pressure supply –case 1
• 2 supply pipe risers branch to
supply cold water to sanitary
fittings on each floor.
• Another riser branches to
feed hot water storage
cylinders on each floor.
• Most economical- grouping of
sanitary fittings on each floor.
• Works best in buildings with
service core e.g., office
buildings.
Main pressure supply –case 2
A 10 storey apartment building
with 4 flats on each floor.
• A pair of risers supply cold
water outlets and hot water
cylinder to each flat on each
floor.
• If a pair of risers are used to
supply 2 flats on each floor-
equalisation of flow will not be
achieved.
• Suited for apartment buildings.
2 Pumped and Main pressure supply
• When main pressure supply
is insufficient pumps are
installed.
• 2 main supply pipes from
main to lower floor levels.
• 2 main supply pipes with
pressure from pumps in
basement/lower level.
• Operation of pumps
controlled by Pneumatic
pressure vessels.
3. Multiple risers
• 1 rising supply pipe branches
to supply 3 lower floors and
then rises to supply 3 upper
floors.
• 1st Supply reinforced by
second rising supply which
leads to upper 3 floors.
• 2nd Supply reinforced by third
rising supply.
• Suitable for multiple
occupancy and varying
demand.
4. Gravity feed cold water supply
5. Low level storage cistern
• Cistern at lower level
• Pumped supply to upper
levels from the cistern.
• Operation of pumps
controlled by Pneumatic
pressure vessels.
6. Zoned Supply system - Intermediate level storage cistern
• Supply divided in to zones.
• Cistern at lower and
intermediate level.
• Intermediate level storage
cistern acts as pressure
breakers.
• Equalised pressure and
Uniformity in flow is
achieved by using
pressure breakers,
pressure release valves
and boosters.
Intermediate level storage cistern
Intermediate level storage cistern
https://www.youtube.com/watch?v=PgxSD6H799Q
STORAGE CAPACITY
The quantity of water to be stored shall be calculated taking into account
the following factors:
a) hours of supply at sufficiently high pressure to fill up the overhead
storage tanks;
b) frequency of replenishment of overhead
tanks, during the 24 h;
c) rate and regularity of supply; and
d) consequences of exhausting storage particularly in case of public
buildings like hospitals.
If the water supply is intermittent and the hours of supply are irregular, it
is desirable to have a minimum storage of half a day’s supply for
overhead tanks.
NOTE—General guidelines for calculation of capacity of these storage
tanks are as follows:
a) ln case only OHT is provided, it maybe taken as 33.3 to 50 percent
of one day’s requirement;
b) In case only UGT is provided, it maybe taken as 50 to 150 percent
of one day’s requirement; and
c) In case combined storage is provided, it may be taken as 66.6
percent UGT and 33.4 percent OHT of one day’s requirement.
Water Supply Requirements for Buildings
Water Supply for Residences
A minimum of 70 to 100 litres per head per day may be considered adequate for
domestic needs of urban communities, apart from non-domestic needs as flushing
requirements.
As a general rule the following rates per capita per day may be considered
minimum for domestic and non-domestic needs:together with full flushing
Out of the 150 to 200 litres per head per day, 45 litres per head per day may be taken for
flushing requirements and the remaining quantity for other domestic purposes.
Water Supply for Buildings Other than Residences
Minimum requirements for water supply for buildings other than
residences shall be in accordance with Table 1.
Types of pumps
The common types of pumps are
• Positive displacement pumps
• Centrifugal pumps
• Turbine pump
• Submersible pump
• Jet pumps (ejector)
Positive displacement pumps
• Reciprocating pump and
• Rotary pump
Selection of pumps
The factors that determine the selection of pumps are
• Rate of yield of the well
• The daily flow needed by the users
• The size of storage or pressure tank used
• The total operating pressure (the height to which the water must
be raised)
The two critical determinants are
• Flow rate
• Total pressure (head) includes the suction shaft, static head and
friction loss
ESTIMATION OF PIPE SIZES
A reasonable rate of flow from outlets (taps, valves) can be achieved by
estimating the pipe sizes.
Depends on
1. Static or pumped head of water pressure.
2. The resistance to flow of the pipes.
3. Fittings and bends.
4. Assumed frequency of use of outlets.
1. Rate of flow.
Rate of flow at outlets depends on
• Diameter of the outlet
• Pressure of water at outlet
• water pressure available at source
• Loss of pressure due to friction resistance of pipe
• Loss of pressure due to friction resistance fittings such as elbow,
tee, taps.
1 gpm =3.78 litre/m
1 gpm =0.063 litre/s
2.Static or pumped head of water
pressure.
• water pressure is expressed as
hydraulic or static head
• Static head is the vertical
distance in metres between the
source, cold water storage
cistern and the tap or outlet.
• Static head is the pressure
available to provide a flow of
water against the frictional
resistance of the pipe work and
fittings.
• frictional resistance is expressed
as loss of head for unit length of
pipe.
3. Loss of Head.(frictional resistance to flow)
• Loss of head depends on the pipe diameters and various material
in use.
• Frictional resistance to flow of fittings such as elbows, tees,
valves and taps is large in comparison to the length of pipe.
• Frictional resistance of fittings is expressed as a length of pipe.
4. Assumed frequency of use of outlets.
• Unrealistic and uneconomical to assume that all outlets will
be in use simultaneously.
• Assumption of frequency of use of outlets is necessary to
estimate the required pipe sizes.
Calculation of pipe sizes
Assumption of pipe sizes
• Calculate a rate of loss of head in the index pipe run.
• Actual length of pipes + estimated likely length of pipe due
to resistance of pipe fittings.
1. Actual length of pipes in
1,2,3 & 4 is 9.5m.
2. Assume an equivalent
length of 50% i.e.,5m.
3. Total equivalent length =
9.5+5= 14.5 (say 15m).
4. The head is 2m.
5. The permissible rate of
loss of head is 2/15 =
0.13 per meter of
equivalent length of pipe.
6. The rate of loss of head
should not exceed this
value at any point.
0.13 against 1.98 falls Between 35 and 42mm .
If we select 35mm then the rate of loss of head will be
Greater than 0.13. Hence we need to take 42mm.
Calculation of pipe sizes
Actual H/L interpolated
From graph for 1.98
2/ 22.6 =0.09 against 42 dia
0.085 x 7.3 = 0.62
References
1. Benjamin Stein & John S. Reynolds : Mechanical and electrical equipment for buildings .Nineth
edition,2000.
2. National Building Code of India, Bureau of Indian Standards, Second revision,2005.
3. Barry: The Construction of Buildings, Third edition, Volume 5.
4. [Source : http://www. grundfos.com]
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