PORTABLE TOILET FOR
EMERGENCY SANITATION RESPONSE
Technical Drawings, List of Materials, Assembly Instructions, Field
Checklist, Decommissioning Guidelines, Adaptations for Local
Conditions, Common Repairs, Design Calculations
Emergency Sanitation & Portable Toilet Concept
What is a Portable Toilet?
- Technology for Safe Excreta Disposal that can be easily transported & quickly
constructed to provide culturally appropriate sanitation facilities in an emergency situation
Why a Portable Toilet?
√ Need for rapid response (24 to 72 hours) to provide sanitation to large numbers of
persons in an emergency situation.
√ Can be installed in a day & fully decommissioned in hours.
√ Easy to use at temporary welfare centers when sanitation facilities are needed
immediately, where as masonry construction takes days to implement.
√ Access to Sanitation Facilities is critical for blocking the Fecal-Oral disease transmission
- Rapid Sanitation Response
⇒ Fast & easy to assemble, Construction completed in one day, Little to no skilled
labor required, Efficient to transport- collapsible pieces, Made from locally
- Hygienic, easy to clean
- Safe to use- structurally sound design
- Durable materials for sufficient lifetime until semi-permanent installations are constructed,
able to withstand climate conditions
- Culturally Appropriate Sanitation Method
- Universal Accessibility (elderly, children, women, pregnant person, disabled)
- Simple to decommission- removable & reusable, bury & compost pit
- Environmentally Sensitive- limited wasting of construction materials
Cultural Factors in Eastern Sri Lanka
• The preferred sanitation choice among eastern Sri Lankans is the pour flush toilet.
• Water is typically used for personal hygiene cleaning purposes.
• The traditional sanitation practices include the use of pour flush toilets or open defecation
in jungle, fields, or seaside areas.
• There is typically a high aversion to foul odors from toilets.
• Gender (Male/ Female) should be designated for each communal public toilet.
• Screening in front of toilet areas is preferred to provide privacy
Design Considerations for Portable Emergency Toilet
The Portable toilet can be divided into two distinct parts: Superstructure (above ground) and the
Receiving Pit (below ground). The Superstructure is the “user-interface” of the toilet, while the
Receiving Pit is the “excreta storage & disposal” component.
The Septic Tank & Soakage pit is designed in accordance with the recommendations provided
in the Draft Sri Lanka Standard, CODE OF PRACTICE FOR THE DESIGN AND
CONSTRUCTION OF SEPTIC TANKS AND ASSOCIATED EFFLUENT DISPOSAL SYSTEMS
(FIRST REVISION- SLS 745 : 2003).
2 of 21 version- 15 Sept 2007
A PORTABLE TOILET FOR EMERGENCY RESPONSE
Footprint Roof Area
6'0" X 8'0" Roof Height- Roof Height--->
High side 6" slope Low side 6" slope
4mm Bolt & Nut (3 nos) fixed by Binding wire
see Sheet 1&2
to fix Squatting pan GI pipe 3 4"
to plastic floor slab
E E Pan & Trap 3 1 2"
Air Vent Pipe
C D with Silicone PVC Pipe Sand Bag
E Seal clear 8"
4'-0" (varies) 1'-9"
2" X 2" Timber (4'-0")
2" X 2"Timber (4'-0")
Wooden E E
Planks Welded 4" x 4" Cut 8" X 8" Gully Sucker SECTION A-A
Floor Frame sewarage Access Point
pipe inlet with 12" x 12" Cover
4' x 4' x 15 mm Plywood
C D E Polythene sheet lining
G.L G.L 1' 1' 1' 1'
Plywood 12" x 6"
Plastic Polythene cutaway
4'-0" Overflow Weir
Slab 2" X 2" Timber
(NIC) Horizontal (4'-0") 1'
6'-0" 2" X 2" Timber
A Vertical (4'-0") C D E
8'-0" 25 nos. 1"dia. hole
Plywood Base 6' x 4' 2' x 4' Timber Soakpit Silcone Coating
PLAN Polythene lining Joint Plywood Open Bottom
SECTION B-B SECTION C-C SECTION D-D SECTION E-E
1. Superstructure Assembly See Sheets 1&2
2. Superstructure & Pit may be elevated in cases of high DRAWING TITLE: UNICEF- Batticaloa
groundwater conditions PIT DESIGN & WASH- Emergency Program
3. Air vent pipe for storage pit to be field tested DATE: SCALE: SHEET:
4. Plywood timber supports fixed with 2" and 3" thin nails SITE LAYOUT 05.03.2007 1:50 3/3
3 nos. Frame with 3/4" GI
PORTABLE TOILET FOR EMERGENCY RESPONSE Unicef Batticaloa
Typical Plan of Temporary
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PORTABLE TOILET FOR EMERGENCY RESPONSE
Typical Plan of Temporary
List of Construction Materials
Item Materials Description Unit Q'ty PACKAGE
SUPERSTRUCTURE FRAME (2 frames per 1 set, 2 toilet units per 1 frame)
Amino Sheet 26 gauge (6'-0" x
1 Roof Structure Nos 2
8'-0") with GI pipe Frame
** Walls (3 Side frames)
2 3/4"GI Pipe 9'-6" height Side Frame-right Nos 2
3 3/4"GI Pipe 9'-3" height Side Frame-middle Nos 2
4 3/4"GI Pipe 9'-0" height Side Frame-left Nos 2
5 3/4"GI Pipe 3'-0" length Back Support Nos 4
6 Cabin Cover Nos 2
(UNICEF std dims)
7 Binding Wire Attach tarp & frame kg 0.20
** Doors (2 units, Left & Right side)
Amino Sheet &
8 Door Frame- Right Nos 2
GI pipe Door Frame
Amino Sheet &
9 Door Frame- Left Nos 2
GI pipe Door Frame
10 Nylon String Passive Door Guard m 2.5
** Flooring Materials
11 Floor Frame Nos 2
L Angle Bar & Wood Planks
1"GI Pipe 2'-6" length with
12 Foundation Support Post Nos 12
13 Plastic Floor Slab (Pre-fab) Floor Surface Nos 4
Squatting pan with Trap
14 Squatting Pan Nos 4
15 Self tapping Screws Attach squat pan & frame Nos 12
16 PVC Pipe 3.5" Pipe to pit Nos 2
17 PVC Glue ( 50 g ) Plumbing connection Nos 2
18 Silicone 400 g Seal Trap Nos 3
** Steps: Toilet Cabin Entrance
42 Empty rice bag 50 Kg (4" fill ht.) Entrance step to cabin Nos 4
SOAKAGE PIT 12' x 8' x 4' (1 pit/ 2 sets superstructures 4 toilet units)
** Pit Structure
Plywood 8'-0" x 4'-0"x 15mm Storage Pit Structure (2
1 Nos 2
(Water Proof) sides)
Plywood 8'-0" x 4'-0"x 15mm Storage Pit Top (3 access
2 Nos 1
(3 8"x8" Cuts) holes)
Plywood 6'-0" x 4'-0"x 15mm Storage Pit Structure
3 Nos 1
(Water Proof) (bottom)
Plywood 4'-0" x 4'-0"x 15mm
4 Pit Structure (front, top) Nos 2
5 Plywood 4'-0" x 4'-0"x 15mm Pit Structure (middle panel) Nos 1
Plywood 4'-0" x 4'-0"x 15mm
6 Pit Structure (middle panel) Nos 1
(1'-0" Weir Cut)
Plywood 4'-0" x 4'-0"x 15mm Walls SoakPit- Exfiltration
7 Nos 3
(1" Circular Cuts) Cuts
Plywood 12"x 12"x 15mm
8 Gully Suck Access Cover Nos 3
Plywood 8"x 8"x 15mm
9 Gully Suck Access Plug Nos 3
Polythene Plastic Sheeting Waterproof Lining for
9 kg 14
(500 Gauge) Storage Pit
10 Timber 2"x 2" x 4' (Pine) Timber Supports for pit Nos 26
Timber Supports for Joining
11 Timber 2"x 4" x 4' (Pine) Nos 4
Water Seal for Exfiltration
12 Silicone 400 g Nos 2
13 Thin Nail - 2" Attach Timber to plywood Kg 1.25
14 Thin Nail - 3" Attach Timber to plywood Kg 1
** Ventilation Pipe
15 "L" Bow - 2" Air vent pipe Nos 1
16 Pipe - 2" ( 12 '-0" ) Air vent pipe Bar 1
17 Air vent Cap 2" Air vent pipe Nos 1
18 PVC Mesh Net (vector control) Air vent pipe Sq.ft. 0.5
Support Timber Posts
19 Air vent pipe Nos 1
(2" x 2" x 8' )
RECOMMENDED ITEMS- NOT INCLUDED IN PACKAGE
1 Mammoty Digging pit Nos 2
2 Shovel Digging pit Nos 1
3 Hand Saw Cutting plywood Nos 1
4 Hack Saw Frame Cutting GI pipe-adjustment Nos 1
5 Hack Saw Blade Cutting GI pipe-adjustment Nos 1
6 Hammer Fitting insert pieces Nos 1
7 Spanner (medium) Bolt tightening Nos 1
8 Alascoor Tarp & plastic slab holes Nos 1
TOILET CLEANING KIT
1 Toilet Bucket (9L Plastic) Flushing & Cleaning Nos. 2
2 (Plastic with Nylon Brush) Toilet Cleaning Nos. 2
3 Soap & Plastic Case (Dettol ) Handwashing Nos. 2
4 (Phynol 5L) Toilet Cleaning Nos. 1
5 Broom Cleaning of Toilet Area Nos. 1
6 Rubber Gloves Toilet Cleaning Nos. 1
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PHOTO STEP GUIDELINES & RECOMMENDATIONS
√ Select site in Consultation with responsible local
authorities (PHI, GS, Camp Manager)
√ Avoid contamination of water supply sources (30m)
√ Road Access for Gully Sucker (30m max)
1. Site Selection √ Select Level Ground
√ Avoid lowland Flooding areas
√ Consultation with surrounding users or host families is
√ Excavate pit to 14’-long x 6’-wide x 4’-deep.
√ If groundwater is encountered before reaching 4’, then
2. Pit Excavation - look for alternative location with more clearance to
- if none, it may be necessary to raise the pit,
⇒ 2 laborers + 2 mammoties to excavate
3. Superstructure Frame Assembly
a. Connect Center √ Insert Center Side Frame (¾” GI pipe) into Floor Frame
Side Frame to Floor bushing (1-inch GI pipe)
b. Connect Left & √ Insert Left & Right Side Frames (¾” GI pipe) into Floor
Right Side Frame to Frame bushing (1-inch GI pipe)
√ Slide on Foundation Support Posts
c. Attach Foundation √ Adjust support post length based on desired height of
Support Posts frame
√ Tighten 6mm bolts with spanner
√ Slide ½” GI pipe inserts from the Roof piece into the ¾” GI
d. Attach Roof
pipe Side Frames
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e. Upright the
√ Rotate Frame Structure 90-degrees to upright position
√ Fit the ¾” gi Pipe Back Frame Support into the 1” GI pipe
f. Insert the Back bushings welded to the 3 Side Frame pieces
Support √ Use a hammer to assist with the entry of the Back support
pieces into the bushings
√ Using Claw hammer, exert downward pressure to ensure
full entry of the Roof piece ½” GI pipe inserts into the Side
Frame ¾” GI pipe.
g. Secure Roof √ Verify that roof is secure
√ CAUTION: If roof is not fully secured, then it could
dislodge in a strong wind, which could be dangerous for
the people living in the surrounding area.
Assembled Superstructure Frame
4. Floor Slab, Squatting Pan & Trap
√ Verify that the squatting pan and trap have a good fit.
a. Check fit between The gap at the joint between the pan & trap pieces
Squatting pan should be minimal (less than 5mm).
√ Large gaps could lead to future leaking of excreta.
√ Attach the squatting pan to the floor slab using 3 self-
b. Attach Squatting Pan
tapping screws per floor slab.
to Floor Plate
√ Ensure that connection is secure.
√ Prior to installing the rivots, adjust trap position tight
c. Rivot trap to squatting
against the squatting pan to minimize the gap.
√ Attach trap to pan using 2 Rivots with 180-degree
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√ Insert silicone gel into the joint between the squatting
pan and trap
d. Seal the joint between
√ Smear the gel into the space between the trap and
trap and pan with
pan to ensure that there are not gaps.
silicone √ CAUTION: Any gaps in silicone seal may lead to
leaking of excreta, causing a health hazard.
Completed Floor plate, squatting pan & trap
5. Septic Tank & Soakage Pit Box Assembly
4 x 4 front 4 x 4 1st 4 x 4 2nd 4 x 4 soakpit
8 x 4 side panel (2) 8 x 4 top cover (1) panel & soak compartment compartment side & end
pit top (2) panel (1) panel (1) panel (3)
a. Cover plywood √ Cut polythene to size of plywood panels
sections with √ Attach polythene to plywood with tin tacks
polythene sheets √ Fold polythene around corners and edges
√ Use 2-inch nails to attach 2” x 2” timber supports to
b. Attach vertical 2x2 polythene covered side panels at 2-foot intervals.
timber supports to √ Attach first 2” x 2” support at edge with rectangular
8x4 side panels cutouts.
√ Affix with 2-inch nails.
√ Attach 2” x 4” support timber to end of 8’ x 4’ side panels
c. Attach 2x4 timber and 4x4 soakpit side panels
support at edge of √ Overlap 2” x 4” support timber 2 inches on each side panel
8x4 & connect 4x4 √ Affix with 2-inch nails.
soakpit side panel √ Attach 2” x 2” support timbers to middle and end of soakpit
4x4 panel at 2-foot intervals
d. Build Pit Support √ Follow the series of instructions below to construct
Frame the pit frame & side panels
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ii. Install interior
i. Install Back 4 x4 iii. Install vertical support iv. Install interior support
panel (soakpit) timber on back panel timbers at 2-ft intervals
v. Install Second vi. Install First vii. install 2” x 2” support
Compartment 4’x4’ Compartment 4’x4’ timber in Septic Tank (1st viii. Install Front 4x4 panel
panel panel Compartment)
√ Attach 8’ x 6’ plywood bottom panel to pit frame
N. Attach 8’ x 6’
√ Affix with 2-inch nails.
√ Standing on the pit is not recommended!
6. Septic Tank & Soakage Pit Box Installation
√ The assembled pit box is very heavy.
√ It is recommended to assemble the pit box close to the
a. Move pit box to
excavation to avoid unnecessary movement of the box.
edge of excavation
√ Care should be taken to avoid injury when carrying box
(muscle strain or crushed toes or fingers)
b. Put Pit box on √ Set pit box on edge of excavation
√ Verify that the excavation is sufficient in width & depth.
edge and verify
√ Verify that the base of the excavation is level and uniform
in depth (or slight slope from septic tank downwards to
dimensions soak pit)
c. Set box in √ Carefully lower the assembled pit box into the excavated
excavated pit and pit.
level surface √ If necessary, adjust the base level of the pit
d. Connect 4” PVC √ Ensure 6-inch minimum overlap of PVC pipe end into pit
Sewerage Pipe box.
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e. INSTALL AIR VENT SYSTEM
ii. Apply PVC glue to
i. Assemble elbow, air ii. Attach net over air vent & iv. Attach air vent to vent
secure pieces (gloves
vent cap secure with binding wire pipe & apply PVC glue
iii. Install 2” x 2” x 8’ timber
iii. Cut bottom 12-
ii. Nail Air vent pipe to support outside of pit box & v. Cut opening in top
inches of vent pipe in
2” x 2” timber support Attach vent pipe to support plywood section for Vent pipe
timber with binding wire
√ Backfiill native soil around the external walls of the pit box.
f. Backfill pit box Take care to avoid any voids which could lead to
√ In cases where native soil has low porosity, sand or
compact. aggregate could be substituted to promote exfiltration of
effluent from soakage pit to surrounding soil.
h. Install Top Plywood
g. Prepare Gully
Sections- 8’x4’ and 4’ x 4’
Sucker access point
Insert Gully Sucker Access
i. Cover Top with √ Ensurethattopslabisfullycoveredwithwaterproofpolythenes
Polythene Sheeting heetingtoreducecontactofwaterwiththeplywood.
√ Slight elevation of the pit
j. Cover Pit with is recommended to avoid
excavated soil ponding of rainwater on
the top plywood slab.
√ Standing water can lead
Fully buried pit to water logging &
Elevated Pit weakening of the integrity
of the plywood.
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7. Superstructure Frame Installation
√ Superstructure Frame should be positioned approximately
Frame position in
3 feet (1 meter) from the edge of the pit excavation.
relation to Pit
√ Determine the desired height of the floor frame above the
b. Dig pits for the √ If pit is fully buried the distance between ground level and
the floor frame should be minimized to provide minimum
clearance for the trap and slope for the sewerage pipe.
support posts √ If pit is to be elevated, then determine the height needed
to provide sufficient downward slope for the sewerage
pipe from the trap outlet to the pit inlet.
√ Verify height of Superstructure Frame is sufficient
√ Verify if Superstructure Frame is level
d. Backfill and
√ If position is correct, then backfill the foundation holes with
excavated soil and manually compact soil.
√ Verify stability of Superstructure Frame.
c. Place Floor Plate √ Insert plastic floor slab unit onto the Angle Iron ledge of
inside the Superstructure Floor frame.
Superstructure √ Verify that the floor slab is securely seated onto Angle Iron
√ Install a sand bag between the trap and the ground level
Support Trap with
√ The sand bag will provide support to the pan and trap
during toilet cleaning.
8. Attach Tarpaulin Wall Cover
a. Cut plastic √ Outside Walls (1/2 Tarp per Frame)
tarpaulin √ Center Divider Section (1/6 Trap per Frame)
b. Attach outer
√ Ensure that plastic sheet is fully attached to GI Pipe
tarpaulin to GI pipe
Structure. NO GAPS!
with Binding wire
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b. Attach center
panel tarpaulin to GI √ Ensure that plastic sheet is fully attached to GI Pipe
pipe with Binding Structure. NO GAPS!
√ Tie a 1.25m length of string between the doors, fixing to
9. Attach Door the outside doorframe
retention String √ This string should prevent wind damage to doors and door
hinges from excessive swinging.
√ The Sri Lanka Disability Access standards specify a
maximum step height of 15cm
10. Accessibility √ Efforts should be taken to fill sand bag to this approximate
√ The path to the toilet should also be cleared of bushes and
holes filled to make a smooth entrance.
-> If the total
√ …then it is recommended to install a series of 2 steps.
√ For the 2 step installation, 3 sand bags are needed to form
the ground level is
the pyramid as shown in photo at left. (2 bottom sands
greater than bags, one on top staggered)
√ It is recommended that a safety fence be installed to
restrict access to the soakage pit area.
√ Awareness raising programs through Camp Managers and
11. Safety Fence
Volunteers should be conducted to inform the camp
residents of the dangers of entry (particularly by children)
into this area.
√ Each toilet set contains 4 toilet units, 2 per side, typical
12. Mark Gender & - Male: 2-units side by side
Donor Visibility - Female: 2-units side by side
√ Consultation with surrounding users is recommended to
verify toilet assignments
√ In coordination with Hygiene Volunteers and Camp
Management, provide the Toilet Care Kit Accessories
- Toilet Bucket
13. Toilet Care Kit - Toilet Cleaning Brush
accessories - Soap for Handwashing
- Toilet Cleaning Disinfectant (Harpic, Phynol)
- Rubber Gloves
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Field Inspection Checklist (UNICEF)
Emergency Toilet Installation Checklist
Division/ Location: Start Date:
Camp Code/ Name: Completion Date:
Number of Toilets to be constructed:
Responsible Technical Officer(s):
Names of Laborers:
I. Site Selection
Is toilet at least 15m (50ft) from water supply wells (tubewell or open)?
Is there a water supply source for toilet hygiene water within reasonable walking distance?
Is the pit location accessible for gully sucker truck?
Are toilet locations arranged for 50m max walking distance to shelters?
Is the toilet location safe for use by women and children during day & night?
Is toilet at sufficient distance from shelters or neighbors to avoid complaints of bad smells?
II. Approval of Responsible Authorities
PHI Approval- Signature:
GS Approval- Signature
Camp Manager Approval- Signature:
III. Construction Details
Septic Tank & Soakage Pit construction
Is pit construction in accordance with design drawings?
Is all polythene sheet lining fixed as shown on design drawings?
Are gully sucker hose holes in top slab accessible and easy to find?
Is pit box sufficiently buried to prevent leakage?
Is safety fence in place to discourage entry into Soakage Pit area?
Are welded frame pieces properly fitted? And frame stable?
Is Plastic Sheeting fixed to walls with no gaps?
Are steps installed to facilitate easy entry to toilet?
Is there an external locking system so door is closed when not in use?
Is Privacy sheeting installed in front of door locations?
Is each Toilet assigned to be for Male or Female users? ____ units- Male ____ units- Female
Is UNICEF logo placed on door?
Is Implementing Partner logo placed on door?
V. Toilet Hygiene & Cleaning Accessories
Soap with case for Handwashing
Cleaning Detergent, Broom & Rubber Gloves provided to Camp Manager/ Hygiene Committee
Signature of Responsible Technical Officer: Date:
15 of 21 version- 15 Sept 2007
Common Repairs-Field Testing Results
Field Testing of the Portable Toilet is on-going. To date, UNICEF-WASH team in Sri Lanka, in
partnership with ACTED and IRD, have installed 186 Portable Toilets for Emergency response
during the conflict displacement in Batticaloa District (2007). Currently, the longest duration
installation of toilet is SEVEN months.
• Door hinges: Failure of welds on the door hinge
• Roof: Tearing of the roof tin sheets at the nail cap tops
• Squatting pan: Separation of the squatting pan from the plastic floor slab
• Pit Top Slab: Top plywood slab may weaken over time, expecially if exposed to
standing water conditions.
Adaptations for Local Conditions
1) Privacy Screening
Privacy Screening made from tin sheets or plastic tarpaulin
and timber posts can be installed surrounding the toilet units.
Privacy Screening GREATLY improves the acceptability
of the emergency toilets by the Users.
2) Improved Accessibility
The entry point access to the existing toilet Superstructure can be improved through the
construction of timber stairs or a ramp in accordance with the National Standards for Stair
dimensions and ramp slope.
3) High Groundwater Table
In the event of high groundwater table, the Superstructure and Pit Box can be elevated in
order to provide sufficient storage capacity in the septic tank & Soakage pit. Care should be
taken to ensure that the Superstructure is STABLE andt hat there is sufficient slope of the
sewerage pipe. Additionally, it is recommended that the pit box is buried in sand &
waterproof polythene sheets secured inside the plywood pit box panels in all above ground
areas, so as to avoid the exfiltration of wastewater into the above ground environment.
Access to the area restricted in order to prevent human contact with the fecal matter.
Furthermore, Design Modifications include the installation of a Seepage Trench or Seepage
Bed, as shown in Appendix F & G of the SLS 745 : 2003, Draft Sri Lanka Standard, CODE
OF PRACTICE FOR THE DESIGN AND CONSTRUCTION OF SEPTIC TANKS AND
ASSOCIATED EFFLUENT DISPOSAL SYSTEMS. (See below).
4) Low Soil Permeability
In cases where native soil conditions have low infiltration rates (e.g. high clay content, rock
areas etc.),construction installation of Seepage Trench or Seepage Bed, as shown in
Appendix F & G,is recommended (See below).
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APPENDIX G- SEEPAGE TRENCH SYSTEM
APPENDIX F- SEEPAGE BED
Applicability- Seepage trenches shall be applicable only
Seepage beds shall be applicable only in areas where in areas where the seasonal high groundwater table is
the seasonal high groundwater table is greater than 1.5 greater than 1.5 m below the surface, the soil percolation
m below the surface, the soil percolation rate is between rate is between 25 and 250 mm/hr., and the ground slope
25 and 250 mm/hr., and the ground slope is less than 5 is less than 25 per cent across trenches and less than 5
per cent. per cent along trenches.
Disposal field trenches
1m < Width < 6m
Septic tank Septic tank
Ground slope 25% max.
Ground slope < 5%
Ground slope 5% max.
Length < 20m
Ground surface Perforated distributor pipes
Soil barrier dia.100mm min.
Topsoil Existing surface
Topsoil 100mm min.
75mm min. allowance 75mm min.
Perforated pipe Prepared aggregate
dia.100mm min. 300mm min. (20 – 40mm)
1000mm max. 2000mm max. spacing 1000mm max.
(20 – 40mm) From wall From wall
Level site – slope less than 5 %
TYPICAL ARRANGEMENT OF SEEPAGE BED
TYPICAL ARRANGEMENT OF SEEPAGE TRENCH
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Design Assumptions & Calculations
Storage Tank Design: Portable Toilets for Emergency Response
Objective: Calculate the Design Storage Capacity for Solids & Liquids •
STAGE 1: Volume of Liquid Entering Tank Daily (24 hour Retention Time)
Base Equation: A = P * q_total where A= Volume of Liquid to be stored in Storage Tank
P= Number of People using the Tank
q_total = Sewage Flow per day per person
Let P= 200 Average Number of Persons per Pit (50/toilet, 4 toilets per pit)
q_use = 5 Liters per use for anal cleaning & flushing
n= 1 Number of uses of toilet per person per day
q_total = q_use * n
q_total = 5 Total liters used per person per day
thus A= 1000 liters/ day
STAGE 2: Volume of Sludge & Scum (Maximum Volume prior to Empty)
Base Equation: B=P*N*F*S where B= Volume of sludge and scum
P= Number of People using the Tank
N= Period (years) between emptying of storage tank (Gully Suck Frequency)
F= Sizing Factor (table 6.2, source Franceys, Pickford, & Reed, 1992)
S= Sludge and Scum accumulation rate
(table 5.3, source Franceys, Pickford, & Reed, 1992)
Let N= 0.17 1 empty per 2 months of use (emergency conditions)
F= 1.5 F = 1, when >20C, but 50% increase suggested
due to short storage period and low decomposition
Liters of solids per person per year
S= 25 (25L-toilet only, 40L-toilet+sullage)
B= 1250 liters/ N desludging period
STAGE 3: Required Storage Tank Capacity for Liquids & Soilds
Base Equation: Vl,s = A + B where A= Volume of Liquid to be Stored (24 Hour Liquid Volume)
B= Volume of Accumulated of Solids & Scum at time of Empty (1/2 wks)
Let A= 1000 Liters Liquid per day
B= 1250 Liters of Solids prior to Empty
C= Liters for ventilation
Vl,s = 2250.0 Liters
STAGE 4: Ventilation Space
Base Equation: C = VF * TSA where C= Volume of ventilation required for gas release & scum
VF= Vertical Freeboard above inlet pipe
TSA= Tank Surface Area
Let VF= 6 inches (15cm)
TSA= depends on design
calcs: kelly 03.03.07
18 of 21 version- 15 Sept 2007
Soakage Pit Design: Portable Toilets for Emergency Response
Objective: Calculate the Design Soakpit Capacity for Effluent Disposal
STAGE 1: Selection of Soil Infiltration Capacity Rate (RI)
Table2-1. Approximate clean water and waterwater infiltration rates according to soil type
Engineering in Emergencies, Appendix 20, Emergency Sanitation p.27 (reed & dean, 1994)
Soil Type Clean water Wastewater
medium sand 1500-2400 50
Fine and loamy san 720-1500 33
Sandy Loam 480-720 24
Silt Loam 240-480 18
Clay Loam 120-240 8
Clay Loam 24-120 soak
Table 2-2. Infiltration rate of local material (RI)
Draft Sri Lanka Standard: Effluent Disposal Specific effective area
Perc Rate WW disposal
mm/day mm/hr m2/m3/day
3000 125 6.6
2400 100 8.4
1800 75 11
1200 50 17
600 25 34
STAGE 2: Effluent Volume to be Exfiltrated per Day (VI)
Effluent Volume to be exfiltrated per tank per day
1000 liters per day
1 m3 from sht1, stage 2 calculation
STAGE 3: Calculation of Required Infiltration Area (AI)
Base Equation: AI= Vl * SEA where AI= Infiltration Area
VI= Effluent Volume to be Exfiltrated per Day
SEA= Specific Effective Area of Infiltration
Let VI= 1000 L/day
SEA= Table m2
From Table 2-2. Surface Area
B= 6.6 68 course sand
8.4 87 medium sand Selection for
11.0 113 Batticaloa Conditions
ANNEX: Soakpit Surface Area
Base Equation Ai= base+ 2 sides+ back where Base= base of pit (OPEN)
Sides= Sides panels of pit (HOLES)
Back= Back panel of pit (HOLES)
Let Ai= 87 ft2
SL = SL
Length 6.6 ft
STD Plywood (8' x 4' x 15mm)
4 ft width
3.5 depth (0.5 19 of 21 version- 15 Sept 2007
Storage Tank and Soakage Pit Design: Portable Toilets for Emergency Response
Objective: Analysis of Storage Tank & Soakpit design of Proposed UNICEF-ACTED Pit Design
STAGE 1: Design Criteria
79 ft3 Volume Solid & Liquid Storage
87 ft2 Required Area for Exfiltration of Effluent
STAGE 2: Storage Tank Volume
Base Equation V=A+B+F where A= Volume of Liquid entering tank per day
B= Accumulation of Sludge at time of desluding Proposed UNICEF-ACTED DESIGN
B= 200*N Liters per person per year * N years
Volume of tank V = V_1 + V_2 Let V= (B*W*D)_chamber1 + (B*W*D)_chamber2 4 ft width
Vs,l = 84.0 ft3 B1 = 4 4 ft
W1 = 4 3.5ft L,S
Analysis needed 79.4 D1 = 3.5 0.5 G
provided 84.0 V_1 = 56 ft3
extra 4.6 B2 = 2 4ft 2 ft
W2 = 4
D2 = 3.5
V_2 = 28 ft3
STAGE 3: Soakpit Surface Area
Base Equation Ai= base+ 2 sides+ back where Base= base of pit (OPEN)
Sides= Sides panels of pit (1" perforations) Proposed UNICEF-ACTED DESIGN
Back= Back panel of pit (1" perforations)
Let Ai_mod= (B*W)+2*(B*D)+(W*D) 4 ft width
B= 6 4 ft
W= 4 3.5ft L,S
side walls for
D= 3.5 0.5 G
Ai_mod= 80.0 ft2
Analysis-mod needed 87 calcs: kelly 03.03.07
provided 80.0 reviewed:
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If there are any questions or comments about the content of these Guidelines, Philippe
Barragne-Bigot (email@example.com), WASH Programme Head of Section, UNICEF-
Colombo. please address your comments to Kelly Naylor (firstname.lastname@example.org), Nimaladas
(email@example.com) or Leslie Morris (firstname.lastname@example.org), WASH Programme,
Many thanks to the ACTED & IRD Technical Officers &
“EMERGENCY TOILET TEAMS” for your Commitment &
Creativity in developing & providing Emergency Sanitation
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