Last Thursday morning, the M&E manager of a wastewater treatment plant expansion added us on WeChat. Every time the pump stopped, the outlet pipe gave a heavy "thump" and the flange gasket started weeping — the duty operator didn't dare restart the pump. He said the check valve model was right and the pressure class matched, so where was the problem? In our years providing check valve selection services for SUFA, we get calls like this several times a year. Nine times out of ten it comes down to the same thing: the check valve was selected by size and pressure only, with closing characteristics ignored.
Check Valve Selection Step 1: Know the Three Structure Types
Three types of check valve are commonly used at pump discharges. Swing check valves are the most widely used on horizontal pipelines — low flow resistance and reasonably priced, but they close fast, so the shock when the pump stops is significant. Lift check valves have a short disc travel and close gently, making them better suited to vertical risers and noise-sensitive locations. Slow-closing (cushioned) check valves have a damping mechanism designed specifically against water hammer in large-diameter, high-head pipelines. On sewage mains and at pump station outlets we most often see swing and slow-closing types; in building water supply and other small-bore services, lift check valves are common on risers.
Many purchase lists carry just one line: "Check valve DN300." That's where the landmine is buried. For the same DN300, swing and slow-closing types differ sharply in price, and installing the wrong one in the wrong place is money wasted. Our advice: at the selection stage, specify the installation orientation, media composition, and closing-characteristic requirements all at once. For the structural differences across SUFA's check valve series, get an overview in the product center first, then choose against the pump station drawings.
Water Hammer Isn't the Check Valve's Fault — It's a Closing Mismatch With the Pipeline
Last year at a pump station project, two batches of swing check valves were replaced in succession, yet the water hammer persisted, and the site began to suspect valve quality. We went to look: the valves were fine, the problem was the service conditions — a short pipeline with high head, so backflow developed quickly when the pump tripped, faster than an ordinary single-disc swing valve could cushion. On real projects, this "valve fine, matching wrong" situation appears often.
After switching to a slow-closing valve with staged closing — fast first, then slow — the "thump" disappeared. The lesson: check valve selection isn't about closing as fast as possible; matching the valve to the pump characteristics and pipeline length is what matters.
Check Valves Need More Detailed Parameters Than Butterfly Valves
Wastewater carries particles and fibers, and the disc sealing surfaces wear in ways completely different from clean water; high solids content also demands more erosion-resistant structures and maintenance clearance. So for check valve selection, none of these can be omitted: media composition, size, pressure class, connection method, installation orientation, and working temperature.
If in doubt, send the parameters via the contact us page and we will pick the check valve model from SUFA's product range against your service conditions. Valves ship with a certificate of conformity and pressure test report; verify each item against the contract at acceptance. After-sales support is handled directly by phone and WeChat — we don't leave you guessing from the manual.
A pump station's real costs usually lie not in the valve price but in a single shutdown for repairs. Getting the check valve selection right the first time costs far less than replacing valves afterwards. Before your next pump station tender opens — does your inquiry sheet include a line for closing characteristics?
Suzhou Akameng Automation Equipment Co., Ltd. · Officially Authorized SUFA Distributor (Authorization No. SFSQ-0036) · Tel 0512-66673578 (WeChat 15851489497)