SANITARY INSTALLATION
Design Report
B+7MIXED USE BUILDING
OWENER- W/RO WUBIT GOSAYE
JULY, 2023
SANITARYINSTALLATIONDesign Report
1. Introduction
This report is prepared for the “Sanitary Design of a Mixed Use”. The building
Owned by ATO TARIKU G/MESKEL
Location HAWASSA ,SIDAMA
The design is initiated by the owner of the building requesting the sanitary
Engineer to do the sanitary design for the above-mentioned building. In view of
above, the two entered into a contractual agreement for the sanitary design.
2. Design Approach
Sanitary design of such a building will have two component parts – water supply
system, and wastewater collection and disposal system. And the Design is
carried out by making use of the Ethiopian Building Code Standards for
Plumbing and other International Standards.
Water supply system
A direct system is used and following are the Design steps:
Our water supply source is HWSA .
We get water supply line from AAWSA and we rise up the water supply to water
tanker by using water pump.
Estimation of water demand of the building
Determination of storage capacities for roof water tank
Locating the roof tank
Laying out the internal and external water supply systems
Design of the internal water supply systems
Design of the external water supply system
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SANITARYINSTALLATIONDesign Report
Wastewater collection and disposal system
Design of the wastewater collection and disposal system is carried out using on-
site sanitation system. Following are the design steps:
Laying out the internal wastewater collection systems
Design of the internal wastewater collection systems (adopting separate
collection systems for toilet and non-toilet wastes
Estimation of sewage quantity
Laying out the external wastewater collection system
Design of the external wastewater collection system
3. Design Assumptions
Following are the assumptions made in the design:
a) The number of users is assumed to be THIREE HUNDRED TWO(342)for this
case (for worst scenario)
b) Sufficient pressure head will be available in the municipal water supply
system to lift the water to the roof tank.
c) The size of the roof tank is determined using 2-days storage for there may be
no reliable water supply
d) The diameter of water supply pipes and wastewater pipes is determined using
loading unit and discharge unit methods respectively
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SANITARYINSTALLATIONDesign Report
4. Detail Design
4.1 Storage Capacity of the Roof Tank
The capacity of the roof tank is determined either by the number of users or the
available plumbing fixtures on each floor. The number of users is used in this
design.
--On SEVEN Floor
Number of users = 40 persons
Water demand = 20 liters per person per day
Water required for the floor = 40 x 20 = 800 liters per day.
On SIXTH Floor
Number of users = 40 persons
Water demand = 20 liters per person per day
Water required for the floor = 40 x 20 = 800 liters per day.
-On FIFTH Floor
Number of users = 40 persons
Water demand = 20 liters per person per day
Water required for the floor = 40 x 20 = 800 liters per day.
-On FOURTH Floor
Number of users = 40 persons
Water demand = 20 liters per person per day
Water required for the floor = 40 x 20 = 800 liters per day.
-On THIRD Floor
Number of users = 40 persons
Water demand = 20 liters per person per day
Water required for the floor = 40 x 20 = 800 liters per day.
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SANITARYINSTALLATIONDesign Report
-On Second Floor
Number of users = 42 persons
Water demand = 20 liters per person per day
Water required for the floor = 42 x 20 =840 liters per day.
-On First Floor
Number of users = 42 persons
Water demand = 20 liters per person per day
Water required for the floor = 42 x 20 =840 liters per day.
On Ground floor
Number of users = 58 persons
Water demand = 20 liters per person per day
Water required for the floor = 58 x 20 = 1160 liters per day.
Total daily storage = 6840 liters.
Therefore, storage capacity of the roof tank = 6840 liters; say 10000 liters
4.2 Rising Main
Storage capacity of the roof tank = 10000 liters
Assuming filling time = 120 minutes = 7200 seconds
Rate of filling or discharge = 0.26 liters per second
Using a rising main of Dia. 20 mm, the flow velocity in rising main will be:
V=4Q / πD²=4*0.0003/ (π*0.022)
=0.95 / sec ≤ 1.5 / sec Safe! )
h f=f (LV²/D²g) =0.2mm
Ph= Z+ h fV²/2g
=13 0.2m≤ 16m Safe! )
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SANITARYINSTALLATIONDesign Report
4.3 Pipe Sizing in Building
For Water Supply System
Following is the procedure for pipe sizing:
Draw the pipe systems starting from the roof tank
Calculate the fixtures fed by each pipe
Determine the loading units for each length of pipe
Convert the loading units into design flow rates (liters per second)
Starting from roof tank with known flow rate and velocity, select a diameter
of
pipe. Flow velocity for design of gravity pipe should not exceed 3m/sec
(Preferably less than 1m/sec).
Pipe sizing for the gravity pipe from the roof tank (W1)
HWB Z1 =16 x 0.50 = 1.00
WC Z2= 48x 0.50 = 24.00
)0.5
= 0.25 (1.00 + 24.00)0.5
= 0.25 (25.00)0.5
=3.12 lit/sec
Flow velocity 2.10 / sec 3.0 / sec
V=4Q / πD²
=1.43m/sec ≤ 3.0 / sec
-Therefore, 32 mm diameter pipe is sufficient for the rising main pipe.
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SANITARYINSTALLATIONDesign Report
For Wastewater Collection and Disposal System
Pipe sizing for the vertical stack (S1)
The fixtures and their discharge units
HWB = 16x 1 = 16
WC = 48x 7 = 336
FD = 2x 3 = 6
Total = 352
100mm stack is sufficient for this case as the maximum discharge units loading
allowed per stack is 40 for low-rising buildings.
MANHOLE SIZE DESIGN
Minimum dimensions for inspection chambers & manholes;
Types of access Depth to invert (m) Minimum internal
dimension
Rectangular length &
width (mm)
Inspection chamber or < = 0.6 400 * 400
manhole < = 1.0 600 * 600
< = 1.75 1000 * 75
< = 2.5 1200 * 750
> 2.5 1400 * 900
→ The manholes should be constructed with 25cm thick double brick wall jointed
by cement: sand mix ratio = 1:3 and internally plastered with mortar 1:3 mix
ratios.
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SANITARYINSTALLATIONDesign Report
6. ROOF WATER DRAINAGE
To calculate flow rate from roof, rational method is adopted. Rational formula is
better to estimate flow of catchments area less than 50ha (5km²). The rational
formula estimates the peak rate of at any location in catchments area as a
function off the catchment's area, run-off coefficient, and mean rainfall intensity
for a duration equal to the time of concentration.
The rate of run-off Q (l/s) can be calculated by the following equation
Q = c*A e*I
3600
Where A e is the effective catchments area in m
I is the rainfall intensity (mm/h) for the minimum average recurrence interval in
years and time of concentration.
c is the run-off coefficient
For roof; c=0.75-1
7 DOWN PIPE SIZE DETERMINATION
The size of circular down pipe/outlet/shall not be less than diameter 65mm
/EBCS-9 article 7.4.3.6/
During down pipe size design external factor which might obstruct normal flow
of water considered. Such as:-leaves, bird net and snow will definitely hinder
design flow through down pipe.
Outlets for gutters should be located, where possible, near to each angle; i.e,
where there is a change in direction of flow.
Material of the down pipe is uPVC which is durable and easy for installation.
All exposed down pipes should be painted with UV ray reflective oil paint.
Hence, down pipe size will be calculated as follo
Calculate the gutter size by assuming the following
Gutter is not steeper than 1:350.
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SANITARYINSTALLATIONDesign Report
Gutter has uniform cross section.
The distance between the outlets is less than 100times the diameter of the
outlet.
The width of the rectangular gutter is assumed to be 120mm.
The gutter discharges freely.
The relationship between discharge and critical depth
Q = 9.9 x 10-5 (Ac) 1/2
( Bc) 1/2
Ac = YcBc
Where
Q (l/s)……………… discharge.
Ac (mm²) ………….. Cross-sectional area corresponding to Yc.
Bc(mm)……………..the width corresponding to Yc.
Yc (mm)……………..critical depth.
8.0 Septic tank capacity determination
Assumptions,
People to be served = 342
Average daily water consumption = 80 L/C/D
Hydraulic detention time = 3 days
Average sludge production = 0.15/c/d
Dislodging period = 3 year
Septic tank =Sludge volume + Sedimentation volume
Sedimentation volume = Sedimentation period (day) x Daily water demand (m3)
= 3 days x 0.8m3/day = 2.4m3
Sludge vol. = Total number of users x average sludge pro./day x dislodging period
=(342x 0.15 x 365x3)/1000=56.13m3
Septic tank volume = 56.17+ 2.4 = 58.57
