Septic Design Standard Calculation for 1 or more users

Septic Design Standard Calculation for 1 or more users

Today I am going to teach you that how to design a septic tank for one or more person or septic tank Design Calculation. Most of people construct irregular septic tank for less or more persons. Which is highly cost able?
Here I will make you able to design a perfect and standard septic tank.
Let’s Start!
The quantity of sewage to consider for the design of Septic Tank must not be less than 300 gallons as per standard calculation.
Schematic Diagram of a Septic Tank
I will show you some standard values for one or more bedroom sewage.
Here I will discuss thumb rules for design septic tank for one or more room. Keep it in your mind.

• For one bedroom

For one bedroom septic tank must be design minimum 300 gallon or 371.00 Liters.

For a two bedroom House:

The quantity of sewage to be considering for the septic tank design must not be less than 700 gallons or 2597 Liters.


Let’s begin with an example of a three bedroom residence.

Septic Tank calculations for a three bedroom Residence

The quantity of sewage to be considered for the design of a Septic Tank should not be less than 900 gallons.

As per the thumb rule;

Quantity of sewage to be considered for the design of a Septic Tank = 900 gallons
1 gallon of liquid = 3.78 liters
Quantity of sewage in liters = 900×3.78 = 3402 liters
Volume of Sewage in Cubic feet
3401/28.52 = 119.20 CFT (cubic feet)
Volume of Sewage in Cubic meters
3401/1000 = 3.401 cubic meters

• Dimensions of a Septic Tank in meters:

Width of the Septic Tank = 1.690m
Depth of the Septic Tank = 1.10m
Length of the Septic Tank = 2.10m

• Dimensions of a Septic Tank in feet:

Width of the Septic Tank = 5.71’
Depth of the Septic Tank = 3.34’
Length of the Septic Tank = 6.59’

For one Bedroom house minimum 300 gallons septic tank is very must. For example I want to design a septic tank for 17 persons.
Quantity of sewage to be considered in the design of a Septic Tank = 5100 gallons (For 17 Persons) as per standard calculation of Septic Tank.
1 gallon of liquid = 3.78 liters
Quantity of sewage in liters =5720×3.78 = 21621.6 liters

• Volume of Sewage in Cubic feet

Total Area =133.44 Square Feet
Depth we have 5.5’
Volume of septic Tank is 5.5 * 133.44 = 733.92 CFT

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Last Words!

Thank you for reading this post. If you face any problem in this post then don’t hesitate to ask. Just take at least 300 gallon for one bedroom house. That’s enough for one bedroom house. I have also given you the dimension of septic tank. If you have irregular surface then don’t worry. First find area of the surface and then multiply it with depth of your septic tank. You will get your tank volume. That’s all!