How to Build a Greywater & Urine Infiltration Pit – A Simple, Off-Grid Solution

When using a urine-diverting toilet like the Separett Tiny or Villa, managing liquids responsibly is essential—especially in remote or off-grid locations where municipal sewage or a septic system is not available. One of the most effective and low-tech methods is an infiltration pit. This simple yet efficient solution allows urine and household greywater to safely percolate into the surrounding soil, providing a natural form of filtration.

In this guide, we’ll walk you through the materials, planning, and step-by-step construction of an infiltration pit tailored for 1–4 people.

📍 Choosing the Right Location

• Distance from water sources: The pit should be located at least 10 meters (33 feet) away from wells, springs, or any drinking water source.
• Natural slope: If possible, place the pit downhill from your toilet and greywater source to allow for gravity-fed flow.
• Soil type: Ideal soils are sandy or loamy, which allow for good drainage. Avoid heavy clay soils, low-lying areas, or locations prone to flooding.

📏 Dimensions for a Small Household

For a typical household of 1–4 people:

• Width: 60–90 cm (24–36 inches)
• Depth: 60–100 cm (24–39 inches)

If you expect higher use or year-round drainage in cold climates, consider building larger or multiple pits and rotating their use seasonally.

🧱 Materials You’ll Need

• Coarse gravel or crushed stone
  Size: 15–40 mm (⅝–1½ inches)
  Use clean, angular stones—not smooth river pebbles or pea gravel
• Coarse sand (essential)
  Size: 1–4 mm (about 1/16–3/16 inch)
  Must be free of clay, silt, or fine particles
• Non-perforated pipe
  To connect your toilet’s urine output and any greywater to the pit
• Landscape fabric (optional)
  Helps prevent surrounding soil from clogging the filter layers
• Covering material
  Treated wood, stone slab, or plastic lid for a secure and discreet finish

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🛠️ Step-by-Step Construction

1. Dig the Pit
   Excavate a circular hole with slightly sloped sides to prevent collapse. Recommended dimensions: 60–90 cm wide and 60–100 cm deep.
2. Line with Landscape Fabric (Optional)
   If using, apply landscape fabric to the walls of the pit to minimize soil intrusion into the gravel and sand.
3. Add the Gravel Layer
   Fill the bottom 30–40 cm (12–16 inches) with coarse gravel. This base layer supports drainage and protects the pipe inlet from clogging.
4. Add the Sand Layer
   On top of the gravel, add 30–40 cm (12–16 inches) of coarse sand. This upper filter removes nutrients and particles from the urine and greywater.
   Optional: Add a permeable fabric layer between gravel and sand—but only if it allows water to pass freely.
5. Install the Inlet Pipe
   Route a non-perforated pipe from your Separett toilet’s urine line or greywater outlet. The pipe should end 5–10 cm into the sand layer.
6. Backfill and Cover
   Backfill the remaining space above the pipe with more gravel, then cover with a breathable but secure lid—wood, stone, or metal all work well. A top layer of mulch or straw can help with odor and visual integration.

🔧 Maintenance and Care

• Annual inspection is recommended. If liquids are pooling or draining slowly, consider redirecting flow to a new pit.
• Avoid harsh chemicals or non-biodegradable soaps—they can harm soil microbes and clog the system.
• In cold climates, make sure the pit is deep enough to prevent freeze-ups in winter months.

🌱 Why It Matters

Combining a Separett waterless toilet with a greywater and urine infiltration pit is a simple yet powerful way to live more sustainably. It reduces strain on septic systems, protects natural water sources, and supports eco-conscious lifestyles—all without compromising on sanitation.

Have questions or need guidance for your specific installation? Feel free to reach out to our team at contact.us@separett.com.