Pros and Cons of 2 Check Valves Types

Author: Harry

Nov. 27, 2024

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Pros and Cons of 2 Check Valves Types

One of the most essential valves in water and wastewater pumping systems is the check valve. Its purpose is to automatically open while pumps are running, and return to the closed position to prevent reverse flow when the pumps are not in operation. These valves help minimize energy consumption and protect the pumping system from pressure surges and damage from reverse flow.

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Selecting check valves for a process is like selecting hardware for new cabinets. Once you decide on a knob or a handle, there's a multitude of styles, colors, and price points to consider beyond that. Same with check valves. It's pretty clear the process you're working on requires a check valve, but which one? Each style of check valve is designed to meet a certain need. Here's the pros and cons of two different styles of check valves, the lift check and swing check.

Lift Check Valves

Lift check valves are commonly used in high-rise buildings, industrial and power plant applications, and water and wastewater applications. They have no external moving parts and are known to be economical and reliable. Over time, these types of valves can have high energy costs because the disc remains in the flow stream during operation.

Silent Check Valve

Silent check valves are known for their quiet closure. Flow pushes the disc to allow forward flow. When the pump is stopped, a compression spring pushes the disc into the seat before flow reverses, hence the silent closure.

This type of check valve is most commonly used in clean water applications with high head.

Nozzle check valves are very similar to the silent check valve, are meant for high pressure, industrial and power applications.

Ball Check Valve

Ball check valves are commonly used in water and wastewater applications. They have very simple operation, and are compact and economical too. These valves feature a rubber coated ball that moves in and out of the seat as flow moves forward and reverse.

Because the ball has a long way to travel when the pump shuts off, these valves have a high tendency to slam in high head applications.

Swing Check Valves

Swing checks are certainly some of the most common check valves used in water and wastewater pumping systems. They're readily available and relatively low cost. They're also automatic, requiring no external power source, guided only by the direction of flow.

These valves can come in a few different configurations, operating in the same basic way.

Dual-Disc

This check valve features a wafer body design and two D-shaped discs that rotate out of the way as flow enters the valve. It has good non-slam characteristics, but is not recommended for wastewater applications. It is also susceptible to vibration and wear.

Traditional Swing Check

Everyone knows this one, right? It's definitely the most common check valve in water and wastewater applications. This type of valve usually has metal or resilient seats and a 60-90 degree swing. This valve has a tendency to slam, however, due to the long stroke, friction in the packing, and inertia of the disc.

Air cushions are sometimes employed to help alleviate the slamming. Though some believe that a lever and spring is a better accessory as they allow the valve to close faster.

Tilted Disc Check Valve

The difference between the tilted disc check valve and the traditional swing check valve is that flow is allowed to pass on both sides of the disc. Because of this, it allows for extremely low head loss.

This valve is not recommended for wastewater applications because pins that extend into flow stream tend to collect debris. Clean water or treated effluent are best for this valve.

Do you have the right type of check valve for your application? Could there be a better one? Always discuss changes to your pumping system with an engineer who is well versed in all types of check valves. They may be able to help you find a valve that slams less or could even be more energy efficient.

Not sure if you should change up your check valves? Ask us about it! We gladly provide technical assistance to businesses and municipalities in Wisconsin, Minnesota, Illinois, and upper Michigan.

 

Dual Check Valve (DuC) Backflow Device

Dual Check Valve (DuC) Backflow Device

On May 5, the state regulations (Florida Administrative Code (FAC) Chapter 62) related to protecting the public water supply were changed significantly. 

Every drinking water system in Florida must have a cross connection control program, more commonly known as a backflow prevention program. (See Section 62-555.360 Cross Connection Control for Public Water Systems)
 https://www.flrules.org/gateway/ruleno.asp?id=62-555.360&Section=0

Pursuant to Chapter 50.40 Cross Connection Control Program Code of Ordinances City of Pembroke Pines &#;The minimum backflow protection to be provided and the different categories of facilities that require backflow preventers, as required by the city, are listed in Table 62-555.360-2 of the Florida Administrative Code. Residential Service Connection - DuC Minimum (owned and installed by city personnel when setting the meter) (refurbished or replaced every ten years by city.&#; 
  

 

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Additional reading:
The floating ball valve vs the trunnion mounted ball valve
  • With the State&#;s guidelines for backflow prevention and the City&#;s implemented Cross-Connection Control Program (CCCP) a Dual Check Valve (DuC) backflow device is required at your residence. 
  • When a backflow prevention device is installed, a &#;closed&#; plumbing system is created. This means that any increase in pressure caused by the expansion of heated water may have nowhere to escape.
  • This buildup of pressure may lead to serious consequences such as a ruptured or distorted hot water tank or a collapsed flue within the gas-heated water tank that may lead to the release of toxic gases, such as carbon monoxide.
  • The Florida Building Code requires all plumbing systems that are classified as &#;closed&#; systems have a device installed for controlling pressure.
  • As a result, each resident should have an assessment done by a licensed plumber to determine if an expansion tank

    or

    a combination ball valve and relief valve is required on their system.

For more information on Expansion Tank:

https://usermanual.wiki/Bradfordwhite/BrochureExpansionEtb./view 

 (Information courtesy of Bradford White)

 

For more information on Combination Ball Valve and Relief Valve:

https://www.watts.com/products/plumbing-flow-control-solutions/shutoff-valves/ball-valves/lfbrvm1

  (Information Courtesy of WATTS.) 

Informational purposes only (not a product endorsement)

 

Frequently Asked Questions (FAQ)

 

What Is a Dual Check Valve Device (DuC)?

The Dual Check Valve backflow preventer device is a mechanical device designed to prevent backflow into the residential water system, it consists of two independently acting, spring-loaded check valves and is effective against backpressure and back-siphonage.  The device is only approved for residential service connections. 

What is The Function of a DuC?

In a backpressure condition, the increase in pressure will force the checks to close tighter. If the second check is not working, the first check can act as a backup to stop the backpressure from going through the device.

How will I be notified if a DuC will be installed on my property?

Look for information packet to be hung on your front door handle, followed by a blue door hanger, prior to installation. 

How Is It Installed?


The DuC will be installed in your water meter box by the city or its contractor.

 

What Is Back-Siphonage and Back Pressure?


 

When To Replace and Test The DuC?


This device is subject to failure, as with anything mechanical, so it is required to be replaced at least every 10 years or on replacement of the water meter to ensure the drinking water system is protected. It is not equipped with test ports.

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