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IAMURE International Journal of Mathematics, Engineering & Technology

112

Development of Spreadsheet Program for the Design of Septic Tank for Residential

Dwelling Units

ILDE B. DELORIAORCID No. 0000-0003-3502-448

[email protected] Mindanao State University, Philippines

Abstract - The Revised National Plumbing Code of the Philippines of 1999 requires the use of and construction of septic tank based from the provisions and specifications provided in the code. However, many septic tanks are incorrectly designed and improperly constructed resulting to environmental contamination. Hence, this study developed a spreadsheet program for designing septic tank for residential dwelling units that would aid designers, engineers and master plumbers. The program was developed using MS Excel ® (Office Home and Student 2010 – Family Pack) as it is the most popular and widely used spreadsheet software. The program was evaluated by comparing its output with manual solution. The results indicated that the spreadsheet program can be developed to hasten the design of septic tank. It also provides sketch plans and bill of materials for the said plumbing structure. However, it is recommended to develop other septic design computer programs for apartment and other types of occupancy.

Keywords - ICT, septic tank, plumbing, contamination, spreadsheet, software, program, R and D, Philippines

Vol. 3 July 2012Print ISSN 2244-159X • Online ISSN 2244-1603International Peer Reviewed Journaldoi: http://dx.doi.org/10.7718/iamure.ijmet.v3i1.415Technology Section

IAMURE: International Journal of Mathematics, Engineering and Technology

is produced by IAMURE Multidisciplinary Research, an ISO 9001:2008 certified

by the AJA Registrars Inc.

International Peer Reviewed Journal

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INTRODUCTION

The Revised National Plumbing Code of the Philippines of 1999 defines septic tank as a water tight receptacle which receives the discharge of a plumbing system or part thereof, designed and constructed to retain solids, digest organic matter through a period of detention and to allow the liquids to discharge into the soil outside of the tank through a system of open-jointed sub-surface pipings or a seepage pit meeting the requirements of the Code. John Louis Mouras of Vesoul, France was given a patent on September 1881 and credited with the invention of septic tank.

Septic tank is the most common off-site sanitation in the Philippines. According to the Department of Health (2008), it is estimated that more than 80% of households in the Philippines use septic tanks as their only form of domestic wastewater treatment. Unfortunately, many existing septic tanks, do not comply with the standards set by the Revised National Plumbing Code of the Philippines. Many tanks are incorrectly designed, improperly constructed, poorly maintained and inadequately service. If designed properly, it will remove 40% of BOD and 65% of suspended solids as a result, contaminating the environment. Hence, there is a need to develop a tool that would aid designers, engineers and the like to facilitate and aid in the design a septic tank based on the Revised National Plumbing Code of the Philippines.

OBJECTIVE OF THE STUDY

To develop a spreadsheet program for the design of septic tank for residential dwelling units based from the provisions of 1999 the Revised Plumbing Code of the Philippines.

METHODOLOGY

Theoretical and Design Considerations (Appendix B, sec. B.5, Revised National Plumbing Code of the Philippines)

The provisions stipulated in Appendix B, Sec. B.5 of the Revised


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National Plumbing Code of the Philippines were used as guides and design criteria in formulating the codes for the spreadsheet program. Shown below are the theoretical and design criteria for the design of septic tank for residential housing units.

Table B-2 Capacity of Septic Tank (excerpts – Single Family Dwellings) 1 or 2 bedrooms = 2838 L min. 3 bedrooms = 3785 L 4 bedrooms = 4542 L 5 or 6 bedrooms = 5677.5 L

Extra bedroom = 567.8 L each Compartments = minimum of 2 Inlet compartment= not less than 2/3 of the total capacity of the

tank, nor less than 2 cu.m Width = at least 0.90 m Length = at least 1.5 m Liquid depth = 0.60 – 1.80 m Outlet compartment = min. 1 cu.m - 1/3 of the total capacity of

the tank Septic tanks > 6 cu.m, length of outlet compartment = not less

than 1.5 m Access = at least 2 manholes (0.508 m in min. dimension), if 1st

compartment exceeds 3.7 m in length, additional manhole shall be provided

Inlet and outlet openings = not less than the connecting sewer nor less than 104.6 mm

Inlet, outlet pipe or baffle = shall extend at least 101.6 mm above and at least 304.8 mm below the water surface

Invert of the inlet pipe = not less than 50.8 mm above the invert of the outlet pipe

Side walls = shall extend at least 228.6 mm above the liquid depth Cover of the septic tank = at least 50.8 mm above the back vent

openings Septic tank shall be structurally designed to withstand all

anticipated earth or other loads. Septic tanks shall be constructed of solid materials, not subject to

excessive corrosion or decay and shall be watertight.


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Spreadsheet Software, Design and Writing/Coding

The spreadsheet software chosen was a licensed MS Excel ® (Office Home and Student 2010 – Family Pack) as it is the most popular and widely used spreadsheet software. The design concept consisted of the following:

Input and Output Data Screen Sketch Plans Screen (Simple graphics were utilized to draw

sketch plans of a two-chambered septic tank.) Bill of Materials Screen

The built-in syntax for writing formulas of MS Excel ® were used in coding the formulas and design calculations. All data cells were formatted and validated to ensure that only the desired values are entered into the cells.

Testing and Validation of Program The validity of the program was checked by comparing manual

computations with the program outputs. Discrepancies in the results were used to make the necessary rectifications on the coded program. To test furtherits accuracy, students enrolled in the course ENE-144 (Wastewater Engineering Design) were allowed to use the program for their design plate and were encouraged to report whatever errors they encountered with its usage.

RESULTS AND DISCUSSION

Development of a spreadsheet program for designing septic tank based on the provisions of the Revised National Plumbing Code of the Philippines is possible. Design is facilitated and accurate. Figure 1 shows the resulting Input and Output Data Screen. In this screen, the required design criteria are keyed in and the results are displayed automatically.


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Figure1.Data Entry Menu

The sketch plans of the septic tank consisting of Plan View (Figure 2) and Longitudinal View (Figure 3) can be generated by clicking the “Sketch Plan” button. The plans provide the details of the septic tank showing its required dimensions, labels and structural details. The plans can readily be used as guide in the construction of the septic tank as they show detailed drawing of the required septic tank.


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Figure 2. Sketch Plan (Plan View)

Figure 3. Sketch Plan (Longitudinal View)


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What made this program useful is its ability to generate a bill of materials for the designed septic tank. Construction estimate is a tedious undertaking but by clicking the “Bill of Materials” button, the different materials required in the construction of the tank and its total cost are generated. Prices of the materials can be updated by the user in the program as the cells for the prices are not locked.

Figure 4. Bill of Materials

CONCLUSION

The results indicated that spreadsheet software can be used to develop a powerful utility program for designing septic tank based from the provisions of the Revised National Plumbing Code of the Philippines. The program provides correct and accurate design which ensures that the septic tank is compliant with the provisions of the plumbing code thereby, addressing the problems of septic tanks that are improperly designed and poorly constructed.


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RECOMMENDATION

Based from the results of the study, it is recommended to develop other programs for septic design for apartment and other types of occupancy and consider the development of programs for engineering applications.

LITERATURE CITED

DOH2008 Operations Manual on the Rules and Regulations Governing

Domestic Sludge and Septage. Manila, Philippines.

MS Office Home and Student 2010.

Revised National Plumbing Code of the Philippines of 1999.

Pursuant to the international character of this publication, the journal is indexed by the following agencies: (1)Public Knowledge Project, a consortium of Simon Fraser University Library, the School of Education of Stanford University, and the British Columbia University, Canada: (2) E-International Scientific Research Journal Consortium; (3) Philippine E-Journals; and, (4) Google Scholar.

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