DESIGN OF SEPTIC TANK
The capacity of an area depends on factors like the types of activity, furniture, and
circulation space. For a general estimate, for most buildings, it is 150 kg per square meter. Say,
assume the average person is 75 kg. that works outs about 1 person.
Area per floor to be accomodated:
1st Floor Commercial 800 sqm.
2nd Floor Institutional 800 sqm.
3rd Floor Recreational 800 sqm.
People that can accommodate per flor
1st Floor 800 x 1 = 800 people
2nd Floor 800 x 1 = 800 people
3rd Floor 800 x 1 = 800 people
Total: 2400 people
Assume that 1/4 of the people goes to mixed-use building per day:
2400
600 people
4
Assume that 1/4 of the people uses the toilet per day:
600
= 150 people
4
Total number of septic tank: 2 tanks
Volume of septic tank: The volume of the water tank per person should not be less than
.086 cu.m (refer to table 4-5 Fajardo pg.92)
V = 150 x 0.086
V = 12.90 m3
Assume 1m width per 100 people
W = Number of occupants
x 1.00
100
W = 200
x 1.00
100
W = 2.00 m.
Assume the maximum depth of septic tank liquid 1.50 m.
Solving for the length of the septic tank:
L = Volume of tank
width x depth
L = 12.9
2 x 1.50
L = 4.30 m.
Size of Leaching Chamber
Length of leaching well = L
2
Length of leaching well = 4.5
2
Length of leaching well = 2.25 m.
Total length of the digestion chamber
L = length of septic tank + length of leaching chamber
L = 4.3 + 2.25
L = 6.55 m.
Therefore, the size of a septic tank to serve 600 pople is:
6.60 meters long
2.00 meters wide
1.50 meters deep
DESIGN OF WATER TANK
The capacity of an area depends on factors like the types of activity, furniture, and circulation
space. For a general estimate, for most buildings, it is 150 kg per square meter. Say, assume the
average person is 75 kg. that works outs about 1 person.
Area per floor to be accomodated:
1st Floor Commercial 800 sqm.
2nd Floor Institutional 800 sqm.
3rd Floor Recreational 800 sqm.
People that can accommodate per flor
1st Floor 800 x 1 = 800 people
2nd Floor 800 x 1 = 800 people
3rd Floor 800 x 1 = 800 people
Total: 2400 people
Assume that 1/4 of the people goes to mixed-use building per day:
2400
600 people
4
Based from table 11-3 of Simplified Construction Estimate by Max Fajardo:
Type of Building: Mixed-use Building
1. Water consumption in gallons pe hour per person: 9.20 gal/hour
Note: 1 m3 = 264.2 gallons
2. Volume of water
Volume of water = No. of occupants x water consumption in gallons per hour per person
2
Volume of water = 600 x 9.20
2
Volume of water = 2760 gal/hr.
Convert into cubic meters/hour:
gal 1m3
Volume of water = 2760 x
hr 264.2 gal
Volume of water = 10.45 m3/hr
3. Solve for Diameter and Height of the water tank:
Assume height of the tank = 3 m.
From the formula of cylinder:
V = A xh
V = π x D2
x h
4
10.45 = π x D2
x 3
4
D = 2.20 m
Therefore, the dimensions of the water tank is, 2.20 m in diameter and 3.00 m in height
DESIGN OF SOIL BRANCH
Ground Floor
4 Urinal x 5 units = 20 units
6 Water Closet x 6 units = 36 units
Total: 56 units
Second Floor
4 Urinal x 5 units = 20 units
6 Water Closet x 6 units = 36 units
Total: 56 units
Third Floor
4 Urinal x 5 units = 20 units
6 Water Closet x 6 units = 36 units
Total: 56 units
Total fixture unit: 168 units
Referring to Table 5-2 - Size of Horizontal Fixture Branch and Stack, under column One Horizontal
Branch of "Plumbing Estimates by Max Fajardo", 168 units could be well served by a 125 mm or 5" in
diameter waste pipe.
DESIGN OF HORIZONTAL WASTE PIPE
Ground Floor
10 Lavatory x 1 units = 10 units
8 Floor Drain x 2 units = 16 units
2 Slop Sink x 3 units = 6 units
Total: 32 units
Second Floor
10 Lavatory x 1 units = 10 units
8 Floor Drain x 2 units = 16 units
2 Slop Sink x 3 units = 6 units
Total: 32 units
Third Floor
10 Lavatory x 1 units = 10 units
8 Floor Drain x 2 units = 16 units
2 Slop Sink x 3 units = 6 units
Total: 32 units
Total fixture unit: 96 units
Referring to Table 5-2 - Size of Horizontal Fixture Branch and Stack, under column One
Horizontal Branch of "Plumbing Estimates by Max Fajardo", 96 units could be well served by a 100
mm or 4" in diameter waste pipe.
Second Floor
18 Floor Drain x 2 units = 36 units
Total: 36 units
Third Floor
18 Floor Drain x 2 units = 36 units
Total: 36 units
Total fixture unit: 72 units
Referring to Table 5-2 - Size of Horizontal Fixture Branch and Stack, under column One
Horizontal Branch of "Plumbing Estimates by Max Fajardo", 72 units could be well served by a 100
mm or 4" in diameter waste pipe.
DESIGN OF SOIL BRANCH
For Soil Branch
Ground Floor to Second Floor
4 Urinal x 5 units = 20 units
6 Water Closet x 6 units = 36 units
Total: 56 units
Second Floor to Third Floor
4 Urinal x 5 units = 20 units
6 Water Closet x 6 units = 36 units
Total: 56 units
Total fixture unit: 112 units
Referring to Table 5-2 - Size of Horizontal Fixture Branch and Stack, under column One Horizontal
Branch of "Plumbing Estimates by Max Fajardo", 112 units could be well served by a 125 mm or 5" in
diameter soil stack pipe.
For Waste Pipe
Ground Floor to Second Floor
10 Lavatory x 1 units = 10 units
8 Floor Drain x 2 units = 16 units
2 Slop Sink x 3 units = 6 units
Total: 32 units
Second Floor to Third Floor
10 Lavatory x 1 units = 10 units
8 Floor Drain x 2 units = 16 units
2 Slop Sink x 3 units = 6 units
Total: 32 units
Total fixture unit: 64 units
Referring to Table 5-2 - Size of Horizontal Fixture Branch and Stack, under column One Horizontal
Branch of "Plumbing Estimates by Max Fajardo", 64 units could be well served by a 100 mm or 4" in
diameter soil stack pipe.
Ground Floor to Second Floor
18 Floor Drain x 2 units = 36 units
Total: 36 units
Second Floor to Third Floor
18 Floor Drain x 2 units = 36 units
Total: 36 units
Total fixture unit: 72 units
Referring to Table 5-2 - Size of Horizontal Fixture Branch and Stack, under column One Horizontal
Branch of "Plumbing Estimates by Max Fajardo", 72 units could be well served by a 100 mm or 4" in
diameter soil stack pipe.
DESIGN OF HORIZONTAL WASTE PIPE
Ground Floor
10 Lavatory x 1 units = 10 units
8 Floor Drain x 2 units = 16 units
4 Urinal x 5 units = 20 units
6 Water Closet x 6 units = 36 units
2 Slop Sink x 3 units = 6 units
Total: 88 units
Second Floor
10 Lavatory x 1 units = 10 units
8 Floor Drain x 2 units = 16 units
4 Urinal x 5 units = 20 units
6 Water Closet x 6 units = 36 units
2 Slop Sink x 3 units = 6 units
Total: 88 units
Third Floor
10 Lavatory x 1 units = 10 units
8 Floor Drain x 2 units = 16 units
4 Urinal x 5 units = 20 units
6 Water Closet x 6 units = 36 units
2 Slop Sink x 3 units = 6 units
Total: 88 units
Total fixture unit: 264 units
Referring to Table 11-1 - Maximum Permissible Length of Vents for Soil and Waste Stacks, 264
units could be well served by a 75 mm or 3" in diameter vent pipe as high as 16.8 m.
DESIGN OF FIRE PROTECTION SYSTEM
FIRE HOSE CABINET SYSTEM
THE FOLLOWING ARE BASED ON NFPA 13/14 AND 24
FIRE HOSE CABINET
FHC FLOW RATE (GPM) 50
MAX. NO. OF FHC IN OPERATION AT ANY TIME (NOS) 2
DURATION OF OPERATION (min.) 60
TOTAL STORAGE VOLUME REQUIRED (gal) 6000
TOTAL STORAGE VOLUME REQUIRED (Liters) 22710
TOTAL STORAGE TANK (m³) 34
PUMP REQUIREMENT
PUMP FLOW RATE REQUIRED 100
FHC PUMP HEAD CALCULATION RESIDUAL PRESSURES REQUIRED AT FHC 4
PRESSURE LOSS IN PIPE/FITTINGS & ETC. (BAR) 0.5
ADDITIONAL PRESSURE FOR SAFETY (BAR) 0.5
TOTAL HEAD PRESSURE REQUIRED (BAR) 5
FIRE HYDRANT SYSTEM
FIRE HYDRANT
HYDRANT FLOW RATE (GPM) 250
MAX NO. OF FH IN OPERATION 2
DURATION OF OPERATION (min) 60
TOTAL STORAGE VOLUME REQUIRED (gal) 6000
FIRE HYDRANT TANK STORAGE CAPACITY (GPM) 30000
TOTAL STORAGE VOLUME REQUIRED (LITERS) 113550
TOTAL STORAGE TANK (m³) 114
PUMP REQUIREMENT
PUMP FLOW RATE REQUIRED 500
FHC PUMP HEAD CALCULATION RESIDUAL PRESSURES REQUIRED AT FHC 4.5
PRESSURE LOSS IN PIPE/FITTINGS & ETC. (BAR) 0.5
ADDITIONAL PRESSURE FOR SAFETY (BAR) 0.5
TOTAL HEAD PRESSURE REQUIRED (BAR) 5.5
TANK CAPACITY PUMP CAPACITY
FHC 34 FHC 100
FHC 114 FHC 500
SPRINKLER 154 SPRINKLER 300
SAFETY FACTOR 7 SAFETY FACTOR 50
TOTAL (m³) 309 TOTAL (GPM) 950
FIRE PUMP CAPACITY : 950 GPM AT 8 BAR
JOCKEY PUMP WILL BE 190 GPM AS PER NFPA MAX. 20% OF TOTAL CAPACITY OF FIRE PUMP
DIMENSION OF WATER TANK (m³) 309
8.8 METER DIAMETER AND 7.5 METER HEIGHT
FHC FLOW RATE = 50 gpm
MAXIMUM NO. OF FHC IN OPERATION AT ANY TIME = 2 Nos
DURATION OF OPERATION= 60 mins (ORDINARY HAZARD I)
FHC TANK STORAGE CAPACITY =
RATION AT ANY TIME = 2 Nos
mins (ORDINARY HAZARD I)
