Brief Analysis of Low-Resistance Backflow Prevention Devices

Brief Analysis of Typical Operating Conditions for Low-Resistance Backflow Prevention Devices

The Low-Resistance Backflow Preventer (model: LHS743X) is a critical water quality protection valve for water supply and drainage systems. It employs a dual check valve combined with an automatic intermediate chamber drainage mechanism to create an air barrier, thereby preventing the backflow of downstream sewage or mixed water from contaminating the upstream potable water supply. Compared to traditional pressure-reducing backflow preventers, its primary advantages lie in its lower head loss and superior energy efficiency. Currently, this valve is most widely deployed in three major application scenarios: secondary water supply systems, municipal pipeline connections, and supporting infrastructure for large-scale buildings.

The most commonly encountered application scenario is the secondary water supply pump station in residential complexes—particularly the inlet and outlet pipelines of non-negative pressure water supply systems. In high-rise residential complexes, where water flow rates are high and the water supply margin is limited, excessively high valve resistance can lead to insufficient terminal water pressure. The low-resistance backflow preventer features minimal pressure loss; it not only complies with the mandatory backflow prevention requirements stipulated by relevant codes but also prevents an increase in the overall network pressure loss. Therefore, it is the preferred solution for both new residential developments and the renovation of existing pump stations.

Category II high-frequency application scenarios: municipal water supply network connection points. Where branch pipelines from urban main roads connect to the main supply lines of commercial complexes, industrial parks, schools, or hospitals, regulatory requirements mandate the installation of backflow prevention devices. The municipal water network experiences continuous flow rate fluctuations; however, the low-resistance valve bodies ensure smooth fluid flow, thereby reducing pump energy consumption during long-term operation. This solution is widely applicable to projects involving mainstream pipe diameters ranging from DN80 to DN300.

Third major application scenario: Heterogeneous water system separation. This involves the integration of domestic water supply pipelines with fire-fighting makeup water systems, landscape water features, central air-conditioning circulating water systems, and landscape irrigation pipelines. Such systems often exhibit varying water quality; should a water supply interruption occur and create negative pressure, it can easily lead to backflow contamination. Therefore, backflow preventers must be installed in accordance with water supply and drainage design standards.

In addition, water supply inlet pipes for hotel and commercial building water tanks, as well as water supply pipelines for water treatment equipment, are extensively installed as part of the overall system. For equipment selection, the following considerations apply based on specific operating conditions: for high-risk toxic media, a pressure-reducing type backflow preventer should be prioritized; for ordinary civil water supply systems, high-flow continuous water supply applications, or projects where the existing pipeline network pressure is low, a low-resistance backflow preventer should be prioritized. It is recommended to install the equipment in a horizontal configuration, reserving space for maintenance, and to conduct regular inspections of the drain outlets to ensure the long-term stability of the contamination prevention function.