Check Valve Leaks: Inspect, Avoid, and How to Fix

Figure 1: A large check valve with rust around its cap and body connection point, possibly indicating leakage at one point

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Check valve leaks can cause system inefficiencies, performance issues, and damage. Check valves are meant to allow media to flow in one direction only. However, when the valve leaks due to a worn or damaged disc, seat, or seal, media can leak from the valve or flow in the wrong direction. Identifying and addressing a check valve leak promptly is necessary to maintain a system's efficiency and integrity.

Table of contents

What is a check valve?

A check valve allows media to flow through it in only one direction. This valve operates automatically without the need for an operator. The concept that explains this is cracking pressure. Every check valve has a minimum upstream pressure requirement for the valve to open and allow media to flow past it. The check valve closes when the upstream pressure drops below the cracking pressure, preventing downstream media from flowing backward. Check valves can be specified for a specific cracking pressure. Read our check valve overview article to learn more about how these valves work.

Inspect a check valve

If a check valve has noticeable leaking symptoms, inspecting the valve is the fastest method for determining that it is leaking. Therefore, if check valve leakage is possible, make inspecting the valve a top priority. Before inspecting the check valve, consult the manufacturer's product guide to determine if there are specific steps to take. The following procedure is a general method and may not apply to every check valve model.

• Safety: Conduct a sound inspection (see below) and then depressurize the system before conducting further inspections. Wear personal protective equipment (PPE) such as gloves, safety glasses, and a hard hat if necessary.
• Visual inspection: Look for signs of leakage like moisture, corrosion, and rust around the valve body and pipe connections. Be sure to have a flashlight and an inspection mirror for areas that are difficult to see.
• Touch inspection: Touch around the valve's body and pipe connections with a clean, dry cloth. If the cloth gets wet, the valve may be leaking.
• Sound inspection: If possible, listen to the check valve operating in a quiet area. Normally functioning check valves do not produce sounds. Gurgling or hissing noises can indicate a leak.
• Soap solution test: Use the soap solution test if running gas through the check valve, for example, if there's potential for an air compressor check valve to be leaking. Apply a soapy solution to the valve body and pipe connections. If bubbles form in the solution, gas is leaking.

Figure 2: Regular inspection can help prevent check valve leakage

How to avoid check valve leakage

There are several methods for avoiding check valve leakage or minimizing the risk.

• Correct selection: Select the suitable check valve for the application. This means considering factors such as the valve's material compatibility with the media, pressure and temperature ratings, and the application's flow requirements. Read our chemical resistance of materials guide to assist in selecting a check valve's materials. To understand how to select flow rate, read our Kv and Cv calculator articles.
• Routine maintenance and inspection: With a routine, issues can be identified before they turn into leaks.
• Correct installation: Leaks are almost inevitable if a check valve is improperly installed. Proper installation includes ensuring that the valve is properly aligned with the pipes and in the correct position (i.e., horizontal or vertical), and the system flow direction is the same as the arrow on the valve's body. Read our check valve installation guide for more information on the installation process.
• Worn part replacement: The check valve's seat and disc can wear out over time. Replace them as needed.
• Avoid too much pressure: If the check valve is subjected to pressures higher than it's rated for, it can leak.
• Cleaning and debris removal: If debris gets trapped in the valve, its sealing surfaces can be damaged, causing leaks. Clean the valve and ensure media going through it is free from debris. For example, installing a t strainer or y strainer in front of the valve can prevent debris from clogging it.

Figure 3: Check valves are found in all sorts of environments and should be selected for accordingly

How to fix a leaking check valve

Deciding whether or not to attempt to fix a leaking check valve comes down to the severity of the issue and convenience vs cost. If there is damage to the valve's body, such as severe rust or corrosion, the valve needs to be replaced. However, if damage or wear is only found on internal parts, it's possible to replace the parts rather than the entire valve. Replacing individual parts, though, can be more trouble than it's worth for relatively inexpensive valves, such as those made primarily from PVC. More expensive check valves, such as stainless steel check valves or very large check valves, can be costly to replace, making individual part replacement more desirable.

After reviewing the check valve's product guide for specific instructions, follow these steps to replace check valve components of a leaking check valve.

1. Equip the proper PPE to avoid injury or exposure to hazardous materials.
2. Disassemble the valve to gain access to its internal components.
3. Inspect the check valve's disc, seat, spring, and any other internal components. Look for signs of wear, damage, or debris that may be causing the leak.
4. Identify why the check valve is leaking. Is the problem an internal component such as a worn-out seal or damaged disc? Or is the problem more significant, such as damage to or distortion of the valve body?
5. Replace any internal components that are worn out or damaged. Even if the o-rings appear to be good, take the opportunity to replace them as well.
6. Fully clean any internal components that are not replaced. Clean the inside of the valve body as well.
7. Reassemble and reinstall the valve.
8. Test the valve by gradually introducing pressure into the system. If the repair was successful, there should be no further leaks. If there are leaks, likely the entire valve needs to be replaced.

Additional Information

When it comes to understanding if check valves are supposed to leak, it’s essential to recognize that check valve leaking indicates a problem that needs to be addressed. Ideally, a check valve should not leak. This would compromise the system’s efficiency and could potentially cause damage. Regular inspection and proper maintenance can help mitigate these issues.

However, it is worth noting that some minor leaks can occur due to wear and tear, especially in older valves or in valves that are subjected to harsh operating conditions. Therefore, it's critical to follow the guidelines for selecting, installing, and maintaining check valves to avoid leaks.

In addition, always ensure that the check valve you choose is from a reliable ball check valve supplier to maintain high system integrity.

FAQ

Should a check valve leak?

Ideally, a check valve should not leak. Leakage likely indicates an issue with the valve that will lead to issues with the system.

For further reading on other types of valves and their advantages, read What are the advantages of a gate valve? and 5 Things to Know Before Buying ductile iron pinch valve. Additionally, explore What Advantages Do Three-Way Valve Offer? - automatic valve.

Check Valve Leakage: Inspect, Avoid, and how to Fix

Industrial valves are usually tagged as "zero-leakage" valves but this might not stand true at all times. Some common and simple problems can lead to valve leakage, thus leading to dangerous problems. Leakage is a very critical problem, especially in the case of check valves. Check valve leakage can lead to the sabotage of a system because the purpose of a check valve is quite crucial.

A check valve is employed to make sure that no fluid flows backward. In other words, check valves allow the flow of fluid only in one direction and ensure that there is no backflow. These valves are a cheap and effective solution in systems that require the prevention of backflow.

Check valves produced by industrial valve manufacturer are commonly used in domestic water systems, sewage systems, marine industry, oil and gas industry, and heating systems. When these valves turn faulty, they pose a risk of backflow, and this can be disastrous in situations like a sewage treatment system.

Leakage in check valves can be prevented by checking a few things beforehand. Here are some of the essentials that a buyer has to check before purchasing an industrial check valve to avoid check valve leakage.

Things to Check Beforehand

Classified as one-way or one-directional valves, check valves are primarily employed to avoid the reverse flow of fluids in a system. Not all systems require the same type of check valve – there is a wide range of valves that can be segregated on the basis of their type, function, leakage tolerance, and operating pressure limit. Take a look at these points before choosing the right type of check valve for a system.

• Proper Check Valve Type

Check valves are of many different types – swing check valves, lift check valves, non-slam check valves to name a few. Each of these valves, while functioning as a check valve in general, have unique features that make them the right choice in specific situations.

Here are some of the common types of check valves and their functions.

• Swing Check Valves – These valves allow full free flow of fluids but close automatically when the pressure in the pipeline reduces. Usually paired up with gate valves, these valves attain full closure when there is zero flow.
• Lift-check Valves – With a similar seating position to globe valves, lift-check valves arrive in three body patterns and are best when they are paired up with globe valves. For optimal functioning of this industrial check valve, the flow must enter from below the seat.
• Non-slam Check Valves – Featuring lesser flow resistance, non-slam check valves are designed specifically to withstand water hammering. These valves are employed in several industries including petrochemical industries as they initiate closure without creating excess pressure rise.
• Double-disc Check Valves – In these valves, two half-circle disks are hinged together and they hold open for positive flow and close during reverse flow.
• Tilting Disk Check Valves – Instead of two disks, a tilting disk valve employs a pivoted disk that opens and closes as per requirement. The function of this valve is similar to that of swinging check valves, but these provide a quicker response to pressure differences.
• Leakage Tolerance

As per ANSI standards, there are six different levels of check valve leakage rate. Each level indicated a particular range of leakage acceptable in a valve. Different check valves are produced with varying leakage rates as per their requirement.

These levels are labeled as Classes – Class I to Class VI each has its own standards and settings according to which valves are manufactured. Here is some basic data about these check valve leakage rate levels:

• Class II – Maximum leakage allowed is 0.5% of rated capacity; the capacity is tested by applying pressure to the valve inlet while the outlet is left open.
• Class III – Maximum leakage allowed is 0.1% of rated capacity; the capacity is tested by applying pressure to the valve inlet while the outlet is left open.
• Class IV – Maximum leakage allowed is 0.01% of rated capacity; the capacity is tested by applying pressure to the valve inlet while the outlet is left open.
• Class V – Maximum leakage allowed is 0.005 ml per minute of water per inch; the capacity is tested by applying pressure to the valve inlet after filling the entire body of the valve, connecting the pipe with water, and keeping the valve plug closed.
• Operating Pressure Limit

The specialty of industrial check valves is that they do not need an external control feature like a lever or automation. These valves operate based on the pressure difference across their length and the flow velocity of the fluids. There are many different standards that regulate the operating pressure limit of a valve.

Cracking pressure in valves is the pressure at which the static breaks and flow begin. For check valves, the cracking pressure can be anywhere between 1 and 5 psi. Based on specific requirements, check valves with different cracking pressure levels are manufactured.

Common Check Valve Leakage Troubles and Solution (700-900)

Leakage in check valves happens because of several reasons – it could be due to improper installation, poor maintenance, or even faulty valve manufacturing. Check valve repair is usually done by professionals as they require precision and careful handling. Here are some of the common check valve leakage trouble, their possible causes, and the solution to fix them.

Shut-off Failure

• Description

When a check valve is unable to completely close during zero flow, then this situation might be considered a shut-off failure. Shut-off failure can render the valve useless and result in leakage. Be it in new or old valves, this is a common problem that occurs due to many reasons.

On the other hand, failure of shut-off valves or seizing up is also an issue that occurs often. If a shut-off failure occurs, then the function of the check valve is nulled as the valve will allow backflow. Backflow can be quite dangerous if the valves are employed in chemical and purification environments.

• Possible cause

The possible cause for shut-off failure might be the aging of internal components. Parts like gasket and washers losing their original grip can cause problems in shut-off. It is common for these parts to experience immense wear and tear after continuous usage.

Shut-off failure could also be caused by the obstruction of debris inside the valve. Dirt and debris from the fluids in the pipeline sometimes get stuck inside the parts of the valve and cause shut-off failure.

• How to fix

First, one needs to inspect the industrial check valve to understand what damage has been done. If it is found that the washers are causing the failure of the valve, then the best course of action is to replace the washer.

On the other hand, if the valve is caked with debris, then using a wire brush will be effective. One can also disassemble the valve and clean it thoroughly to avoid any future problems.

Leaks when Closing

• Description

When a check valve is not completely closed, then leakage occurs. Again, the issue could be caused by a variety of reasons. But leakage while closing might also mean that it is time for check valve replacement to take place.

When the proper closing of a check valve does not take place, it results in leakage and backflow. Leaks also open the way for hazardous situations and accidents when the fluid transported is a chemical.

• Possible cause

There are several possible causes for the leakage of a check valve:

1. There might be debris blocking the closing of the valve, causing it to leak.
2. The washer of the check valve could be worn out – this leads to improper functioning of the check valve thus resulting in leakage.
3. Improper installation of the check valve also causes leakage. When the check valve is not the perfect fit for a given situation, there might be more problems than just leakage.

• How to fix

1. If contaminations and debris are the cause of the obstruction and leakage, a thorough cleaning will keep the valve fully functioning.
2. As for the problem with the washer or gasket, it is better to look out for a replacement – washers once worn out cannot be reused because they lose their grip and stop performing their function.
3. Improper installation can be avoided if it is done with proper inspection. Also, if the valve size proves to be a problem, it is better to opt for a check valve replacement.

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