What is the Size of the Sewage Pipe for Mobile Toilets

The most common size for sewage pipes in mobile toilets is dn110mm (110 millimeters), which is the mainstream standard size suitable for the vast majority of scenarios.

I. Pipe Sizes in Conventional Scenarios

1. Single-unit or Low-frequency Use Scenarios
   For single-unit mobile toilets in scenic spots, construction sites, or scenarios with low usage frequency, a dn110mm sewage pipe is a cost-effective choice. This size can meet the daily discharge needs of excrement while considering cost and installation convenience. For sink drainage, a dn50mm (50 millimeters) pipe is typically used, forming a reasonable match with the sewage pipe.

2. Multi-unit or High-frequency Use Scenarios
   In multi-unit mobile toilets in shopping malls, stations, or scenarios with extremely high usage frequency, it is recommended to use sewage pipes ranging from dn110mm to dn150mm. In such scenarios, there is a large footfall and a high volume of excrement discharge. Increasing the pipe diameter can effectively enhance drainage capacity and reduce the risk of blockage. For example, the flow rate of a dn150mm pipe is more than twice that of a dn110mm pipe, enabling it to better cope with peak-hour demands.

II. Pipe Sizes in Special Scenarios

If the mobile toilet is directly connected to a septic tank for direct discharge, the pipe size needs to be adjusted according to the inlet size of the septic tank:

• Discharge Outlet: It is recommended to enlarge it to 250mm to ensure that excrement can be quickly and unobstructedly discharged into the septic tank, preventing blockages or odors caused by residue in the pipe.
• Sink Outlet: It is recommended to enlarge it to 160mm to facilitate the direct flow of sewage into the septic tank and reduce pipe pressure in intermediate links.

III. Scientific Basis for Size Selection

The selection of pipe diameter needs to comprehensively consider flow rate, flow velocity, and frictional resistance:

• Flow Rate Requirements: According to the "Building Water Supply and Drainage Design Standard", the excrement discharge rate of a single-unit toilet is approximately 0.5L/s. The flow velocity of a dn110mm pipe can reach 0.8m/s, fully meeting the demand. For multi-unit toilets, the discharge rate may exceed 1.5L/s, requiring an enlargement to dn150mm to maintain stable flow velocity.
• Anti-blockage Design: The larger the pipe diameter, the stronger the passability of solid particles (such as tissue paper and feces) in the excrement, significantly reducing the probability of blockage. For example, a dn110mm pipe can accommodate solid objects with a diameter of 50mm to pass through, while a dn50mm pipe can only allow particles below 20mm to pass.

By reasonably selecting the pipe size, the drainage system of the mobile toilet can operate efficiently and stably while reducing maintenance costs.