Prevent backflow: Ensures fluid flows only from the inlet to the outlet, avoiding reverse movement.
Protect equipment: Prevents pumps, compressors, and other devices from cavitation or damage caused by backflow.
Reduce water hammer risk: Rapid closing design minimizes shock forces when fluid flow suddenly stops.
Save energy: Avoids energy waste due to media backflow (e.g., in hot water circulation systems).
A check valve controls unidirectional flow through the automatic opening and closing of its disc (or flap). The process is as follows:
Fluid pressure pushes the disc open, allowing media to pass through.
The disc opening angle or height depends on flow velocity and pressure.
When outlet pressure exceeds inlet pressure, the disc closes rapidly under gravity, spring force, or backflow pressure.
The sealing surface tightly fits to completely block reverse flow.
No external control: Operates solely based on fluid pressure changes.
Locking mechanism: Ensures tight sealing when closed to prevent minor leakage.
Check valves are widely used in industrial, residential, and municipal systems. Typical scenarios include:
Function: Installed at pump outlets to prevent water backflow from damaging impellers when pumps stop.
Examples: Fire pumps, water supply/drainage pumps, HVAC circulation pumps.
Function: Isolate different media to prevent hazardous chemical mixing or contamination.
Examples: Oil pipelines, reactor feed systems.
Function: Ensure unidirectional flow of water or gas.
Examples: Water heater inlets, toilet tanks, gas pipelines.
Function: Prevent condensate backflow to protect boilers.
Examples: Steam boilers, thermal pipelines.
Function: Block sewage backflow to avoid pump clogging or pollution.
Examples: Sewage lift pumps, stormwater drainage systems.
Structure: Disc is circular and mounted on a hinge or pivot.
Operation: Forward flow pushes the disc open; reverse flow closes it via gravity or backpressure.
Pros: Simple design, low resistance, suitable for high flow rates.
Cons: Slow closing speed, may cause water hammer.
Applications: Horizontal pipelines, water treatment, low-to-medium pressure systems.
Lift Check Valve
Structure: Disc is disc- or plunger-shaped, moving vertically.
Operation: Fluid pressure lifts the disc open; reverse flow closes it via gravity or spring force.
Pros: Excellent sealing, fast closing, high-pressure resistance.
Cons: High resistance; suitable only for vertical or slightly angled pipelines.
Applications: High-pressure steam systems, boiler feedwater, chemical pipelines.
Structure: Includes a spring to assist disc closure.
Operation: Forward flow overcomes spring pressure to open; spring aids rapid closure during reverse flow.
Pros: Fast closing, effective backflow prevention, installable at any angle.
Cons: Springs may fatigue; requires regular maintenance.
Applications: Pump outlets, HVAC systems, water hammer prevention.
Structure: Compact design with a butterfly-shaped disc.
Operation: Flow rotates the disc open; reverse flow rotates it closed.
Pros: Lightweight, compact, cost-effective.
Cons: Moderate sealing; suitable for low-pressure scenarios.
Applications: Water supply/drainage, food processing, light industrial pipelines.
Structure: Uses a rubber or metal ball as the disc.
Operation: Forward flow pushes the ball away; reverse flow seats it to block passage.
Pros: Simple structure, good sealing, handles particle-laden media.
Cons: Not ideal for high-velocity or high-pressure systems.
Applications: Sewage pumps, slurry transport, agricultural irrigation.
Structure: Flexible diaphragm replaces mechanical discs.
Operation: Fluid pressure deforms the diaphragm to open; reverse pressure seals it closed.
Pros: Corrosion-resistant, leak-proof, ideal for corrosive media.
Cons: Low pressure tolerance.
Applications: Chemical processing, pharmaceuticals, corrosive liquid transport.
| Scenario Requirements | Recommended Type | Reason |
| Low-pressure, high-flow pipelines | Swing or Butterfly Check Valve | Low resistance, cost-effective |
| High-pressure or vertical pipes | Lift or Spring-Loaded Check Valve | High sealing, pressure resistance |
| Corrosion or sanitary scenarios | Diaphragm or Ball Check Valve | Corrosion-resistant materials, easy cleaning |
| Rapid closure needs | Spring-Loaded or Axial Check Valve | Minimizes water hammer, fast response |
A: Check valves rely on unidirectional disc movement. Reverse installation prevents proper opening/closing, causing failure, backflow, or equipment damage. Ensure the valve’s arrow aligns with the flow direction.
A: This is caused by water hammer. Solutions:
① Use slow-closing valves (e.g., spring-assisted types).
② Install water hammer arrestors or air chambers.
③ Adjust system flow velocity to avoid sudden stops.
A: Depends on the type:
Lift Check Valve: Must be vertical (relies on gravity).
Spring-Loaded: Any angle, including vertical.
Swing Check Valve: Typically horizontal; vertical installation requires special design.
A: Common signs:
Backflow: Reverse media movement (e.g., drained outlet pipes after pump shutdown).
Leakage: Seepage when closed (check seal wear).
Jamming: Disc fails to open/close (debris or corrosion).
A: Yes! Frequency depends on usage:
Household: Annual checks for seal integrity and component mobility.
Industrial: Clean discs and inspect springs/hinges every 3-6 months; shorten intervals for high-pressure/temperature systems.
A: Choose based on media:
Water/air: Cast iron, brass, stainless steel (304/316).
Corrosive liquids: PTFE, PVC, Hastelloy.
High-temperature steam: Cast steel, chromium-molybdenum steel.
A: Ideally, a well-sealed valve blocks backflow. However:
Micro-leaks: May occur due to seal wear or debris.
Delayed closure: Brief backflow if the disc resets slowly (use rapid-closing types).
A: No! Their functions differ:
Check Valve: Automatic one-way flow control; no manual flow adjustment.
Shut-off Valve: Manual on/off or flow regulation; no backflow prevention.
A: Recommended! Benefits include:
Preventing hot water backflow into cold pipes (saves energy).
Avoiding tank drainage during water outages (protects heating elements).
Recommended types: Spring-loaded or ball check valves (compact, easy to install).
A: Depends on material, media, and usage:
Household: Brass/stainless steel lasts 5-10 years.
Industrial: High-strength alloys with maintenance: 10-15 years.
Corrosive environments: Special materials (e.g., PTFE) may last 3-5 years.
