DN250 (10″) Class 300 ASTM A216 WCB Flanged Swing Check Valve CH057602

Sizing a check valve is based on flow rate and allowable pressure drop. A common mistake is simply matching the pipe size — this often leads to an oversized valve, causing the disc to flutter and wear out prematurely. An undersized valve creates excessive pressure drop and restricts flow.

Evaluate your system’s minimum and maximum flow rates, then consult the manufacturer’s Cv data to select a size that operates efficiently across that range. As a rule of thumb, the valve should run at 60%–80% open under normal conditions. Also consider fluid viscosity — thicker fluids need larger ports. When in doubt, contact our technical team with your system specs for a verified recommendation.

Water hammer occurs when flow suddenly stops or reverses, and the check valve disc slams shut against the seat, creating a high-pressure shockwave that travels through the piping system. This is often caused by using a valve that closes too quickly for the system’s flow velocity, or by installing a swing check valve in a long piping run where reverse flow velocity builds up before the disc fully closes.

To prevent water hammer:

1. Choose a “silent” or “non-slam” check valve — these feature a spring-assisted disc that begins closing before the flow fully reverses, avoiding rapid impact against the seat.

2. Consider a slow-closing check valve or a valve with an external dashpot or dampening mechanism that controls closure speed.

3. Ensure the valve is correctly sized — oversizing increases the distance the disc travels, worsening slam; proper sizing keeps the disc near the seat at normal flow.

4. For pump discharge applications, a combination of a check valve and a control valve with a controlled ramp-down can eliminate water hammer entirely.

If you are experiencing water hammer in an existing system, start by verifying that the flow velocity does not exceed 10–15 ft/s (3–4.5 m/s) for liquid services — this is often the root cause.

Yes, but it depends on the type of check valve. Most spring-loaded check valves can be installed in any orientation, including vertical, because the spring assists disc closure regardless of position. However, swing check valves rely on gravity to return the disc to the seat, so they are typically recommended for horizontal pipelines only. If a swing check valve must be installed vertically, flow direction must be upward to assist the disc in closing properly when flow stops.

Other types have different constraints:

• Lift check valves are generally suitable for vertical lines with upward flow

• Wafer or dual-plate check valves often allow vertical installation but check the manufacturer’s specification

Always review the manufacturer’s installation instructions for specific orientation requirements before ordering.

Cracking pressure is the minimum upstream pressure required to just open the valve and allow flow. It is a critical selection parameter because it determines the pressure threshold at which the valve will operate. If your system has a low inlet pressure, a check valve with a cracking pressure that is too high will not open, starving the downstream system. Conversely, too low a cracking pressure might lead to premature opening or disc flutter.

As a general rule, choose a check valve with a cracking pressure of approximately 10% to 20% of the minimum operating pressure of your system. Spring-loaded check valves typically have higher cracking pressures than swing or silent check valves, which rely on gravity or flow dynamics. Always verify this parameter against your system’s low-flow conditions — especially during startup or turndown scenarios.

The core difference lies in their function and operation. A check valve is an automatic, self-actuating safety device that allows fluid to flow in only one direction to prevent backflow — it requires no manual intervention and operates entirely based on line pressure. A ball valve, on the other hand, is a quarter-turn manual or actuated valve that an operator uses to start, stop, or throttle flow — it does not respond to system conditions automatically.

In practice, these two valves serve complementary roles and are often installed together. A ball valve upstream of a pump provides isolation for maintenance, while a check valve downstream prevents reverse flow when the pump shuts off. Using one as a substitute for the other is a common design error: a ball valve left partially open offers no backflow protection, and a check valve cannot be used to shut off flow for service.

If you are selecting a valve for a pump discharge line, you will typically need both — a ball valve for isolation and a check valve for backflow prevention. They work together, not in competition.