Ventilation of pits for toilet blocks

  • phreymon
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Ventilation of pits for toilet blocks

Dear all,

I am currently looking at the design of school toilet blocks in Tajikistan. Ventilation is a general problem in the visited school latrines, even in the new ones. The common design (from Soviet times) is a number of drop holes (usually around 10 - 5 for boys and 5 for girls) over a single huge holding tank. At best, there is one or two ventilation pipes. Not surprisingly, the smell in these toilet blocks is very bad, and is a major hindrance for their use. Clearly, the sparse chimneys do not generate the necessary air aspiration that would improve the climate in the toilet block.

My impression is that to improve ventilation, the holding tanks should be divided in smaller compartments, with one compartment and one ventilation pipe per 2 toilet holes maximum. However, I would like to have feedback on that. Did any one do a study on the topic (optimisation of ventilation design in toilet blocks) or have practical experience to share?

Thanks in advance and best regards,

Philippe Reymond
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  • goeco
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Re: Ventilation of pits for toilet blocks

Hi Philippe, have you considered a small solar extraction fan in the ventilation pipe to ensure there is always a vacuum through the latrines? It shouldn't take much to create sufficient negative pressure so the smell doesn't escape outwards into the latrine.
cheers
Dean

Dean Satchell, M For. Sc.
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  • phreymon
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Re: Ventilation of pits for toilet blocks

Hi Dean,

Thanks for your answer. I have to check the availability, cost and robustness of such a system in Tajikistan. For now, I was rather thinking of rotary chimney cowls.

Any idea on the compartmentalization of the holding tank?

Cheers,

Philippe
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  • JKMakowka
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Re: Ventilation of pits for toilet blocks

If you go for active ventilation, compartmentalization would make things more difficult no?

However assuming the climate in Tajikistan can be quite cold, any kind of active ventilation in an unheated toilet can make it very uncomfortable to use due to the draft it creates at the drop-hole.

Maybe it is better to improve the ventilation of the cubicles themselves and provide a lid for the drop-hole?

Or maybe an upgrade to a simple water seal would be the best solution after all?

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Re: Ventilation of pits for toilet blocks

Hi Philippe,
Not sure of your exact climatic conditions, but a rotary cowl would only work when there is wind... I would imagine the latrines smell more in still, warm conditions? Is it only cold at night? Are the latrines mostly used during the day? Do the toilets mostly smell when the weather is warmer? The choice with solar extractor fans is either direct attachment of fan to panel, in which case the fan would only work during the day, working better in warmer conditions when the sun is shining and in the middle of the day, or alternatively a battery is used so the fan is running constantly. You should be surprised how cheap this equipment is and keep in mind you will only need a very small fan.



This image is of a solar vent that moves about 25 CM of air per hour in direct sunlight and costs about $50 US and is simply attached to the top of your chimney.

cheers
Dean

Dean Satchell, M For. Sc.
Go-Eco Sustainable Solutions
www.go-eco.co.nz
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  • phreymon
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Re: Ventilation of pits for toilet blocks

Thanks both for your inputs.

These are school toilet blocks, so used only during the day, in a country rather dry and sunny! The solar vent could be a good option.

The holding tanks are very big, type 4m width x 6 m length x 2 m depth. Not sure if one or two chimneys, as is usually the case, are sufficient to attract all the air in the right direction, even with the solar vent. Hence the idea of making smaller compartments.

Simple water seal will not work, as there is almost never water at the toilet block. Having a functioning handwashing facility is already a challenge. I was thinking about SaTo pans, but without any water for cleaning after use, it will not work either.

Best,

Philippe
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