5 Things to Know Before Buying ductile iron Air Valve

Author: Adelaide

Mar. 31, 2025

Top 10 questions you should ask when purchasing a control valve


Automatic control valves, much like everything else we purchase these days, are not all created equal. Some fall into the high quality bracket with pricing to match, while others hover closer to the lower quality and price sensitive end of the scale. Unfortunately, when evaluating control valve prices, it is not always clear what you are being offered and what standards the valve actually meets. Here are a few questions to consider and ask the supplier to ensure you get years of trouble free operation that lasts longer than it takes the sales person to drive out of your parking lot!

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Q 1 What materials are being used?

Make sure you know what the different components of the valve are made of, as this will certainly affect the life of your valve, specifically:

Body Material – is the valve body cast iron or ductile iron? Traditionally valves were cast iron but ductile iron has become the new standard due to its superior physical properties that are much better at weathering the elements.

Body Coating – Most of the world insists on fusion bonded coating of a valve, inside and out. Unfortunately here in North America, that is not always requested. This just makes common sense for valves that are constantly wet and sit in locations that are not always dry and pristine. A valve should last for many years, so insisting on a coated valve is a wise choice.

Seat Material – bronze is typically the common material for seats but over time, depending on water quality and velocities, bronze wears resulting in the need for replacement. This is time consuming and expensive as seat replacement requires a complete disassembly of the entire valve. Ideally go for stainless steel.

Valve Internals – Most valve manufacturers utilize stainless steel for their valve stems. Make sure that you ask what grade of stainless you are getting as not all stainless steel is created equal. 316 SS is always the best choice because it is harder and least likely to corrode.

External Fasteners – Over time valves experience condensation or flooding and this can play havoc with coated studs or bolts. There is nothing worse than trying to remove heavily rusted studs out of an old valve to perform maintenance. Request stainless steel fasteners as this will ensure that bolts will be removable at any age.

Q 2 Does the valve supplier fully understand your application?

Too frequently a specification will be requested and a valve is supplied that is simply the wrong valve for the job. It may also be the case that there is just a better solution. Ensure you give your valve supplier all the necessary pressure and flow details including details of the actual application and what you want this valve to do. Having the wrong valve for the wrong application, at best case will result in a significantly shorter life and worst case, a malfunction that can result in destruction of the valve and other parts of your water distribution system.

Q 3 Will this new valve fit into my existing piping layout?

Don’t be tempted to just stay with brand X because that is the valve you may be replacing and has the same lay lengths. Most manufactures can be quite innovative on providing solutions to combat varying lay lengths so explore all of you options rather than just settling because you think it may be easier.

Q 4 Do you need specialty tools for maintenance?

Nobody wants to have to carry around a specific tool that only performs one task. Ensure that your valve can be maintained with everything you would carry in regular tool kit. Some valve manufacturers require specialized seat removal tools, or vice jaws installed with copper jaws to protect valve stems. While these are great ideas, they are certainly not things that the average operator has in his toolkit.

Q 5 Will your personnel receive complimentary factory qualified training?

Control valves are not so difficult to understand and once taught, most operations personnel can easily perform maintenance. Ensure that you will not be reliant on the additional cost of having to bring out a factory person every time your valve requires maintenance. Request that a factory-trained representative is on site when the valve is commissioned. This will allow your operators to be schooled in the regular maintenance needs, know what to look for if things go awry and how to start up a valve in a new system or after service. Simple tricks like removing air out of the pilot system are valuable lessons to see in practice.

Q 6 Does your valve have a solid warranty?

These days having a product with the long term back up of the factory is important. Three years should be the standard to ensure there are no manufacturing faults.

Q 7 Can I make changes to the valve if required

Having a valve “expansion ready” for the future can save you money and make your decisions a whole lot easier. For example, can you add a limit switch or a position indicator easily? Or, if you need to move the pilot system to the other side of the valve, can you do it, or is it not possible because the valve body does not have the required connections? Things always change and a flexible valve gives you more options to keep your now perfect valve, perfect down the road.

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Q 8 Does your valve meet industry standards?

There are third party accreditations that ensure your valve was built to the correct specifications. For example; NSF 61, WRAS, UL/FM, AWWA, ISO et.al. They are important because they ensure that the valve has been built to a given standard so the user can be assured they meet approval for such things as low lead content, bacterial growth tests, functional tests etc.

Q 9 Do you have local and factory support?

Make sure there is someone in the area that is factory trained and available to come out and assist when you have questions or problems. This sounds like a given but it’s best to ensure the local agent will in fact be there for you when you need him. When a valve fails, timing is usually of the essence so you should know whom to call prior to such an event.

Q 10 Is the valve solution offered able to handle future needs?

In the world of “low bid wins”, a supplier may be tempted to squeeze as small a valve as possible into the application in order to reduce price. Make sure that the offered solution will supply your needs for the foreseeable future without the burden and additional cost of having to change a valve in a couple of years.

Cast Iron, Ductile Iron, Bronze and Stainless Steel Valves

Not all valves are built the same and there’s good reason for that. Knowing a few basic facts about the different materials will ultimately have long-term effects on your application’s capabilities. Cast iron, ductile iron, bronze and stainless steel are all similar metals but what stands each of these apart? We’ll assist you in choosing the best metal solution for your everyday valve application needs.

Cast Iron

Cast iron — a metal made from mostly iron with small amounts of carbon and silicone — is known for its tolerance to extreme temperatures. It can handle temperatures over 2,100 degrees Fahrenheit. It is a very strong metal and can usually go undamaged through situations of intense vibration; however, cast iron is extremely rigid and has a low resistance to bending. Almost any bending will cause the material to fracture or break completely. A big advantage to cast iron is the cost. It is a relatively inexpensive metal and a very economical and useful option for most situations.

Ductile Iron

Ductile iron, as its very name suggests, is more flexible than cast iron. It is an iron alloy made with nodule-shaped graphite crating a metal that has a little more room to bend without breaking or cracking. With the ability to flex, however, comes a lower overall temperature tolerance than cast iron and a slightly higher cost.

Valves built from ductile iron have excellent corrosion resistance and superb strength, making it a great choice for applications in which a tougher material is needed and in conditions where weathering is likely. Here at Flomatic all of our ductile iron valves are epoxy coated to protect the valves from long term erosion and corrosion in many different fields of application.

Bronze

The use of bronze in plumbing systems dates back to the Roman Empire. Made primarily from copper and tin, this metal is both strong and malleable. It does not crack as easily as iron as it has high ductility. Bronze is also known for its high resistance to corrosion even against harsher fluids and those similar to seawater. However, the nature of the alloy causes it to have a somewhat rough and porous surface which can leave the material susceptible to pitting and degradation over time if not properly maintained.

It is important to note that consumers should seek out valves with the lowest lead content. Make sure if you’re picking out a bronze valve for potable water, you’re choosing a valve that is ANSI/NSF 372 & ANSI/NSF 61 certified. These certifications mean it meets the minimum lead requirements for safe and healthy drinking water.

Stainless Steel

Stainless steel has become a very popular valve material for many reasons. Valves made from this metal have exceptionally high oxidation and corrosion resistance and extreme durability, making a product that lasts a long time. Stainless steel valves do not rust, even if placed in areas of high moisture or directly in water. This property makes them a great choice for coastal regions where saltwater corrosion may be a concern.

The smooth metal is easily cleaned, and a popular choice for food and beverage applications. Stainless steel has good heat resistance; however, it is not ideal for extreme high-temperature applications. A potential downside of stainless-steel valves is that they’re very expensive. However, with price, comes high-quality.

What do these terms all mean?

Using the information provided above, think about your scenario and the conditions in which the valve will be used. Will it be outdoors? In severe temperature? Will this metal be susceptible to movement and vibration? Once you determine the extremes, you’re easily able to choose the appropriate metal for your application.

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