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Pit latrines

Pit latrines are probably the oldest as well as the crudest method of sewage disposal around. Dating back to antediluvian times, the modern pit latrine can be quite a smart structure with ventilation, moulded seat and ablution facilities contained in an air-conditioned man-made capsule. A large percentage of the world’s population rely on these devices for their creature comforts. However, unlike the flushing first world ‘porter loos’, they are mostly makeshift rural affairs erected with scrap materials by the poor people of the district.

What they are

A typical long drop ‘hole’ is 700mm x 700mm x 1m deep. It should be deeper, but anyone who tries to dig a hole this size will understand why: it’s very cramped, the earth is hard and you battle to swing a pick to loosen the sub-soil. Then again, planks of wood more than 900mm long are expensive – and the ‘bog’ is really the last place a poor man with a hungry family to feed will spend money. Many authorities supply subsidized cubicles (typically made of fiberglass) that have seats moulded into them.

The first ‘deposits’ are often accompanied by a rotting chicken’s head or similar in the mistaken belief that this will start the sewage break-down process by introducing sewage-devouring maggots. Such a pit will probably last the average five person family for a year, depending on the quantities of household refuse thrown in by others. Urine keeps the dry sludge moist, permitting the motility of latent microorganisms within the faecal mass.

How they work

Natural bacteria in the urine-pasty fluid slurry of faecal sludge degrade the volume of COD over time into:

  1. Natural gasses, which escape via the hole in the seat
  2. Water, which slowly seeps through the five faces of earth into which the (conventionally) rectangular hole has been excavated.

Microorganisms latent in the surrounding soil will progressively ‘polish’ the seeping fluid even further, returning it ultimately to potable quality before it re-joins the subterranean water table.


Pit latrines are frequently provided to service…

  • Municipalities - informal settlements, overspill residential areas;
  • Farming - field toilets for convenience of labour;
  • Environmentally sensitive locations - for visitors and tourists;
  • Formal rural housing - family toilets;
  • Cabins and cottages - for infrequent visitors (often precursor to a septic tank).

Pit toilets are not advised...

  • On rocky terrain where seepage may be insufficient;
  • Heavy clay soils where seepage could be impaired and they will fill rapidly;
  • Districts (usually alluvial plains) where water table levels are ‘high’.

The fact that social factors obscure the observance of all or some of the above is one of the reasons for poor health in sub-economic rural and ‘over-spill’/squatter areas – usually in peri-urban locations crowded by people lured by the potential availability of employment.


For those considering the provision of pit toilets, warnings should advise that...

  • No foreign objects, other than human wastes, to be deposited;
  • 'She bins' (serviced frequently) be provided;
  • Good quality toilet tissue – that will degrade readily – be provided.

Common pit latrine problems

Due to spillage and incomplete biodegradation, the average pit toilet is a noisome facility. However, this condition can be improved by adding a couple of buckets of laundry water (containing detergent residues of Nitrates and Phosphates) twice a week. This also helps with the distribution of bacteria within the faecal sludge. Slight pooling of water enables visual inspection for bubbles – made by biogasses as the faeces degrade – which indicate that the pit is working.
There are four main reasons for pit latrine failure:

  1. Too many people using the toilet (especially added accommodation, permanent friends etc.);
  2. Rough paper, plastic bags and bottles being thrown into the pit;
  3. The use of harsh chemicals to counter odour – this is a bad mistake because the latent bacteria that occur naturally are killed off, the faecal mass builds up and the odour worsens, attracting flies that may carry and spread dangerous diseases;
  4. The dumping of kitchen wastes into the toilet – pit latrines should only ever receive human body wastes.

Pit latrine management

  1. Nearly all pits will benefit from dosages of our product BIO-SYSTEMS PLR. The great advantage of using BIO-SYSTEMS PLR is that the product introduces a strong, virile ‘army’ of natural sewage bacteria. Selected for their ability to work in dry, anaerobic conditions these microorganisms degrade human sewage as fast as possible while out performing any pathogens (hazardous bacteria) that could otherwise become dominant and be spread to the community by flies and other insects, to the detriment of public health.
  2. We suggest 1 x soluble sachet a week or so after the commissioning of the pit toilet (to ensure there is ‘food’ for the sewage microbes), followed by 1 x 25g sachet every three months, or as dictated by frequency of usage during seasonal gatherings. Common sense tells you that if more people use it, the pit will fill faster and so you need more ‘bugs’ to degrade the contents. PLR will degrade FOG in sewage fairly rapidly, but it is the cellulose components – especially in high-fibre rural diets – that take longer to break down and cause a more rapid rise in the sludge level.
  3. Regarding spillage, urine usually contaminates the seat and floor causing ammonia odours that attract vermin, especially flies. This can be overcome by scrubbing with BIO-SYSTEMS HSDG, which will loosen and encapsulate the ammonium compounds without hurting the biomass of bugs or the person undertaking the cleaning. BIO-SYSTEMS HSDG is a very hard working product that, when used as directed, will keep pit latrine surface areas odour and stain free.
  4. Some authorities specify ventilated pit toilets for ecologically sensitive sites where ground formation and/or non-availability of tankerage makes pit toilets the only option for the convenience of visitors. Social niceties for people accustomed to more civilized disposal systems demand the application of BIO-SYSTEMS L2120 liquid which counters odour generated in the pits by the faecal sludge.

Pit latrine before treatment

Pit latrine after treatmentPit latrine before treatment

Pit latrine after treatment
(note the bubbles indicating biological action)

We at BIO-SYSTEMS SA are able to advise on pit latrine design and placement. Please enquire at

Click on the BIO-SYSTEMS Product table for a complete list of products. Also see our Pit latrine case histories.

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