How can building drainage pipes cope with the problem of "negative pressure blockage"?
Publish Time: 2025-10-10
In modern buildings, the stable operation of the drainage system is directly related to the occupant experience and the long-term safety of the building. However, in high-rise or densely populated buildings, an often-overlooked yet significant problem—"negative pressure blockage"—is quietly threatening the smooth flow of drainage systems. "Negative pressure blockage" is not a physical obstruction within the building drainage pipes, but rather an imbalance in air pressure generated during the drainage process, leading to poor water flow, a breach in the water seal, and even sewage backflow.
1. The Formation Mechanism of "Negative Pressure Blockage"
When a large volume of water rapidly flows from a high-rise building into a riser, a high-speed column of water forms within the building drainage pipes. This column of water acts like a piston, compressing the air below as it moves downward, while simultaneously creating a localized vacuum above—a "negative pressure zone." This negative pressure draws water from the traps in the drainage branch pipes. Once the water seal is breached, sewage odors, bacteria, and even harmful gases can enter the building, seriously impacting environmental hygiene. More seriously, excessive negative pressure can hinder the smooth discharge of subsequent water, slowing water flow and causing drainage problems. It can even produce gurgling sounds or bubbling, giving the illusion that the building's drainage pipes are clogged. This is known as "negative pressure blockage."
2. Common Scenarios for Negative Pressure Blockage
This problem is most common in high-rise buildings, especially residential and public buildings 15 stories or higher. The taller the building, the longer the drainage riser, the greater the potential energy of the water flow, and the more significant the negative pressure effect. Furthermore, periods of concentrated water use within the building can exacerbate this problem. Improper drainage system design, such as insufficient ventilation, undersized pipes, or the lack of dedicated vent pipes, significantly increases the risk of negative pressure blockage.
3. Core Countermeasure: Proper Ventilation System
The key to resolving negative pressure blockage lies in balancing the air pressure within the building's drainage pipes. The most effective approach is to establish a comprehensive ventilation system. Common practices include:
Roof-mounted vent pipes: Extending the drainage riser to the rooftop, where it connects to the atmosphere, ensures that the air pressure within the building drainage pipes remains consistent with the outside world, effectively relieving negative pressure.
Dedicated vent risers: For high-rise buildings, roof-mounted venting alone is insufficient to cope with complex operating conditions. Independent vent risers are required, connected to the drainage pipes via ring or appliance vent pipes to achieve dynamic air pressure regulation.
Self-circulating venting technology: When rooftop venting is not possible or the building's design restricts it, a self-circulating venting device can be used. This device allows air to circulate back through its internal structure, preventing negative pressure buildup.
4. Optimizing building drainage pipe design and material selection
In addition to the venting system, the layout and material of the building drainage pipes themselves are also crucial. Ensure that the slope at the junction of the drainage lateral branch pipe and the riser meets the specified requirements to avoid air blockage. Using pipes with smooth inner walls can reduce water flow resistance and mitigate air pressure fluctuations caused by turbulence. In addition, the use of new pipe fittings such as swirl tees or special Suvito joints can guide water flow down the pipe wall in a spiral, reducing the water tongue effect and effectively alleviating negative pressure.
5. Strengthen Maintenance and Intelligent Monitoring
Even with a perfect design, problems such as vent pipe blockage or water seal drying may occur after long-term use. Therefore, regular inspections of vent pipe patency and maintaining floor drain water seals are essential maintenance measures. In recent years, with the development of smart buildings, some high-end projects have begun to incorporate building drainage pipe pressure sensors and intelligent monitoring systems to monitor pressure changes in the drainage network in real time and provide early warning of potential risks.
This poses a substantial threat to the healthy operation of building drainage pipes. This problem can be effectively avoided through scientific ventilation system design, optimized pipe layout, selection of advanced materials and accessories, and ongoing maintenance and management.
