An aqua privy is not much different from a septic tank. The difference is that the latrine/s is located directly over the tank.
• The excreta enter it directly from the latrine through a drop pipe.
• This pipe is submerged under water inside the privy.
• This water directly acts as the water seal for one or more latrines opening into it.
A septic tank can treat wastewater from both the kitchen and the toilet, while an aqua privy is designed to handle only toilet waste.
Basic Design
• The system has a watertight chamber filled with water.
• A short drop pipe from the latrine extends into the water, creating a seal that blocks odors.
• The tank can be circular or rectangular, and its size depends on how many people use it.
• For a small family, a 1-cubic-metre (35 cu.ft.) tank is sufficient, needing cleaning only every 6 or more years.
• Larger versions are also built for public use.
How Waste Breaks Down
Waste is treated through anaerobic digestion (anaerobic microbes break down waste without oxygen).
• This process produces gas, so a vent pipe is needed to safely release it above rooftops.
Important Safety Notes
• The liquid waste (effluent) is not safe—it still contains harmful bacteria and parasites.
• It must be treated further, just like septic tank waste, using methods like:
o Subsoil irrigation (letting it soak safely into the ground)
o Absorption systems (filtering it through soil or sand)
• Over time, sludge builds up at the bottom and must be removed periodically.
Aqua privies are a practical, low-maintenance solution for sanitation, in areas without sewer systems.
Advantages over septic tank:
• Cheaper and less maintenance: as the required land area is lesser.
• There is a lower risk of toilet blockages since drop-pipes carry waste directly from the toilets into the tank—allowing for tissue paper use without major issue
Disadvantages over septic tank:
• Need more water as the drop pipes have to remain submerged
• Aqua privy handles only toilet waste whereas septic tank can receive and treat wastewater from kitchen and bathrooms too.
References:
• Guide 30, Developing Knowledge and Capacity in Water and Sanitation. WEDC website. Available from: https://wedc-knowledge.lboro.ac.uk/resources/booklets/G030-Septic-tank-a... Accessed on 29th April 2025.
• Park's Textbook of Preventive and Social Medicine. 26th ed. Jabalpur: M/S Banarsidas Bhanot; 2021. Environment and Health; p. 799-883.
• Park's Textbook of Preventive and Social Medicine. 27th ed. Jabalpur: M/S Banarsidas Bhanot; 2023. Environment and Health; p. 832-915.
• Bhalwar R. Textbook of Community Medicine. 5th ed. New Delhi: Wolters Kluwer; 2023. Chapter 8, Excreta Disposal; p. 89-101.
Sanitation Barrier: https://ihatepsm.com/blog/sanitation-barrier-keeping-our-communities-hea...
Excreta Disposal: https://ihatepsm.com/blog/proper-excreta-disposal-necessity-health-and-d...
Video on Sewage Treatment: https://youtu.be/M3iMq4-iFHg
Bore-Hole Latrine: https://ihatepsm.com/blog/bore-hole-latrine#google_vignette
The Dug Well Latrine (Pit Latrine): https://ihatepsm.com/blog/dug-well-latrine-pit-latrine-more-practical-al...
Borehole vs. Dug-Well Latrines: A Comparison: https://ihatepsm.com/blog/borehole-vs-dug-well-latrines-comparison
Water-seal Latrine: https://ihatepsm.com/blog/water-seal-latrine
RCA Latrine: https://ihatepsm.com/blog/rca-latrine
Septic Tank: How it Works: https://ihatepsm.com/blog/septic-tanks-how-do-these-work
Aqua Privy: https://ihatepsm.com/blog/aqua-privy-how-does-it-work
Aqua Privy: https://ihatepsm.com/blog/aqua-privy-how-does-it-work