Mobile Toilet Septic Tank Construction

The construction of mobile toilet septic tanks should follow the following steps and key points:

I. Site Selection and Planning

1. Location Requirements: It should be located away from building foundations (outer wall distance from the exterior wall of the house ≥ 5 meters), drinking water sources (≥ 100 meters), and main roads (≥ 20 meters). Choose an area on the downwind side of the dominant wind direction of the housing, with slightly higher terrain and firm soil, ensuring convenient vehicle access for cleaning and emptying.
2. Standard Basis: According to the 'Urban Environmental Sanitation Facilities Setting Standard' (CJJ27-2012), the distance between the septic tank and buildings should not be less than 30 meters. In actual operation, adjustments should be made based on the terrain and usage requirements.

II. Excavation of Foundation Pit and Foundation Treatment

1. Size and Slope: The size of the foundation pit should be at least 50 centimeters wider than the perimeter of the tank, with a depth greater than the height of the tank and a 200-millimeter cushion space reserved. The pit walls should be sloped at an angle of 30°-50° to prevent collapse. If groundwater is encountered, a sump pit should be excavated for drainage.
2. Cushion Construction: After the original soil at the bottom of the pit is compacted in layers, a 20-centimeter-thick sand cushion should be laid and compacted, or a 20-centimeter layer of gravel should be laid first, followed by a 10-centimeter-thick C20 concrete cushion.

III. Tank Installation and Fixation

1. Hoisting and Alignment: Use a level to align the tank horizontally, with a deviation of no more than 5 millimeters. Immediately fill the tank with water to half of its volume after it is in place to prevent displacement or floating during backfilling.
2. Sealing Treatment: For combined tanks, special adhesive strips, screws, or mortar should be used to seal the socket connections, recessed and protruding grooves, or flange plate connections.

IV. Pipe Connection and Sealing

1. Slope Control: The slope of the inlet and outlet pipes should be 1%-3%. The connections should be tightly sealed with sealant and rubber sealing rings, and micro-expanding waterproof cement mortar should be applied on both the inside and outside.
2. Position of the Sewage Pipe: In a three-chamber septic tank, the sewage pipe opening from the first chamber to the second chamber should be located at one-third of the effective depth of the first chamber, and the opening from the second chamber to the third chamber should be located at half of the depth of the chamber. The vent pipe should be at least 2 meters above the ground.

V. Backfilling and Compaction

1. Layered Backfilling: Use manual backfilling with plain soil or fine sand, removing stones. It is strictly prohibited to use machinery for direct earth pushing. Compact each layer to the designed elevation after backfilling.
2. Special Scenarios: In Anyang area during winter, insulation cotton should be wrapped around the outside of the pipes to prevent freezing and cracking. Backfill with sand and gravel to 5 centimeters above the pipes, and then compact in layers with yellow soil.

VI. Acceptance and Maintenance

1. Sealing Inspection: Before the first use after installation, empty the impurities in the tank and observe whether the drainage is smooth and whether there are any leaks.
2. Regular Maintenance: Check the pipe sealing every quarter and clean the sediments. Ensure that the connecting pipes comply with local environmental protection requirements to avoid direct discharge of sewage.