Installation of Mobile Toilet with Septic Tank

The installation of a mobile toilet with a septic tank should follow the steps below to ensure safety, environmental protection, and functional compliance:

I. Preliminary Preparation and Site Selection

1. Site Selection Requirements
   • Keep away from building foundations (minimum distance ≥ 5 meters, standard requirement ≥ 30 meters) and drinking water sources (≥ 100 meters), avoiding the upwind side of prevailing winds, easily polluted areas, and groundwater recharge zones.
   • Prioritize areas with slightly elevated terrain, firm soil, and good drainage to ensure easy access for cleaning vehicles.
2. Tools and Materials
   • Tools: Shovels, tape measures, wrenches, spirit levels, etc.
   • Materials: PVC pipes, sealing rings, rubber gaskets, micro-expanding waterproof cement mortar, sand and gravel, loess, concrete, or bricks, etc.

II. Excavation and Foundation Treatment

1. Excavation Dimensions
   • The excavation should be at least 50 centimeters wider than the septic tank on all sides, with a depth greater than the tank height and a 200-millimeter cushion space reserved. Common excavation depths are about 1.2 meters, with a diameter 20 centimeters larger than the tank.
2. Bottom Treatment
   • After layered compaction of the original soil at the pit bottom, lay a 20-centimeter-thick sand cushion or crushed stone + a 10-centimeter-thick C20 concrete cushion. Alternatively, a 10-centimeter-thick sand and gravel cushion can be used and compacted to ensure tank stability.

III. Septic Tank Installation and Fixation

1. Tank Hoisting
   • After hoisting, immediately calibrate with a spirit level, ensuring a levelness deviation of ≤ 5 millimeters, and fill the tank with water to half its volume to prevent displacement or floating during backfilling.
2. Connection of Modular Tanks
   • Connection points such as bell mouths and flanges should be sealed and fixed with special adhesive strips, screws, or mortar to ensure no leakage.

IV. Pipe Connection and Sealing

1. Inlet and Outlet Pipes
   • Align PVC pipes with the tank's inlet and outlet ports, secure them with sealing rings + glue, and control the slope between 1% and 3%.
2. Odor and Leakage Prevention
   • Install anti-overflow valves and seal connection points tightly with sealant and rubber gaskets, applying micro-expanding waterproof cement mortar on both the inside and outside.
3. Sewage Pipes (for three-chamber septic tanks)
   • The pipe from the first chamber to the second chamber should be located at one-third of the effective depth from the bottom, and the pipe from the second chamber to the third chamber should be at half the depth of the chamber.
4. Ventilation Pipes
   • Install firmly, extending at least 2 meters above the ground.

V. Backfilling and Compaction

• Backfill sand and gravel in layers up to 5 centimeters above the pipes, then compact with loess, avoiding impact from stones on the tank. Direct mechanical backfilling is strictly prohibited to prevent tank deformation.

VI. Commissioning and Acceptance

1. Drainage Test
   • Open the inlet valve to check for smooth drainage and confirm no leakage.
2. Impurity Removal
   • Empty impurities from the tank before first use to prevent blockage.

VII. Use and Maintenance

1. Regular Inspection
   • Check pipe sealing and clean sediments every quarter.
2. Winter Freeze Protection
   • Wrap insulation cotton around pipes to prevent freezing and cracking.
3. Compliant Discharge
   • Ensure connected pipes comply with local environmental protection requirements and prohibit direct sewage discharge.