Septic Tank Design

Septic tanks are systems that convert waste from toilets into biodegradable products to be released to the environment without harm.

They are designed with 2 chambers.
The 1st chamber has buffer walls to prevent non bio degradable objects from flowing to the drain pipes, leading to clogging and blockage.
The 2nd chamber allows for the waste water to be biodegraded into non foul smelling water which is then released into the environment through the drain pipe into soak pits.

Soil pipes at the 1st man holes enable foul smelling gasses to be released into the atmosphere at a level higher than the roof where none will be affected by the smell.

Time period.

Well designed septic tanks can last up to 15 years without the need to be repaired or emptied.
Grey water from the kitchen and bathroom, which contains anti biotic/antiseptic soap, should be drained seprarately and directly into the soak pits since the soap can render the septic tank inefficient.


The size of a septic tank is determined by the number of people the septic tank is to serve. In buildings with the new water-saving toilet types, less water used means that the septic tank will last longer.

The soak pit area should be as large as possible to enable seepage of the waste water into the surrounding soil.

In land where there is not enough space for septic tank and soak pit, a bio digestor is more efficient and suitable.

The anaerobic bacteria digest the waste in the septic tank and the soak pit area. On average, the waste takes 2 days though the septic tank into the soak pit area, a time which is sufficient to break it down into safer components for absorption into the environment.

In areas with poor drainage soil eg black cotton soil, its advisable to fill in the soak pit with large sized quarry chips to make the soakage faster.

For more info feel free to contact the below

Architect Francis Gichuhi Kmamau.

Arch. Francis Gichuhi Kamau. (337 Posts)

Architect Francis Gichuhi . B.Arch. University of Nairobi. Registered Architect, Kenya. Member, Architectural Association of Kenya. Contacts. email Telephone +254721410684


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