OK. You know you need a valve to complete your project, but if you aren’t a professional plumber or engineer, you might not be sure which will work the best.
Don’t worry, we’re here to help you find the right valve.
Just answer the questions in the next few blog posts and you’ll be a lot closer to your decision. We are going to talk about valve purpose, material, pressure and sizing, as well as a few other things that will help make the decision easier.
Unfortunately, the world of valves is wide ranging, with more specialty valves than you can shake a stick at. Rather than an exhaustive list of every valve variation, we will focus on some the major valve groups and try to get you thinking about the right questions to ask when deciding on the right part.
Valves have two main functions: regulation (control valves) and shut off (shutoff valves).
Determining that aspect of your project can often be the most important part of the decision.
SHUT OFF VALVES
Shut off valves come in plenty of shapes and sizes, but they do what their name implies by completely closing down the flow of liquids or gasses. If your project requires only an on/off capability, a shut off valve is the simplest way to go.
The most common type is a ball valve, which relies on the turning of a lever handle to engage the on/off mechanism, a solid metal ball with a pipe-sized opening drilled through the middle. When the opening aligns with the pipe, flow is possible. When the opening is perpendicular with the pipe, flow is not. Opening the valve partially is not recommended, as that can create cavitation and vibration, causing wear on the valve.
A three-way ball valve is a specialty version of that valve. Sometimes called a “mixing valve,” it allows for both full shut off, redirection of flow from multiple sources and can, in some instances, be used to mix two sources together. (Read about three way ball valves.) Other variations include mini ball valves (which we will talk about later) and varying port/bore sizes.
A second type of shutoff valve is the gate valve. Although sometimes used as a regulating valve, gate valves often use a hand wheel to make the shut off easier. By using a hand wheel on a spiraling track, you gain a mechanical advantage that the lever of a ball valve doesn’t offer. Turning the wheel drives the valve’s stem up or down, bringing the “gate” with it.
That means that much less pressure must be exerted on the valve to make the valve close and that it can be closed incrementally, easing stress on the pipes and avoiding damaging “water hammer.” That incremental shut off gives rise to people using the valve as a regulator, although most engineers advise against this use, as it can cause greater wear and may cause leaks over time.
With the exception of a lever-type “quick shut off” gate valve, gate valves take longer to close than ball valves, which usually only require a 1/4 turn.
One thing to consider when deciding on whether to use a gate or ball valve is “clearance” for the valve to be manipulated. In close quarters, a gate valve might be the best option, because you do not need as much space to turn the wheel as you do to switch a lever.
If quick shut off capability is necessary, a ball valve might be the right choice. Mini ball valves are good for smaller areas, because their levers do not extend beyond the valve body. But as the name implies, mini ball valves aren’t always large enough to get the job done. It is unusual to find mini ball valves larger than 1” NPT.
Control valves, sometimes known as “regulating valves,” allow the user to select the amount and/or the direction of flow through a plumbing system, either manually or automatically, in the case of check valves.
Control valves come in a variety of designs. Some of the most common manual control valves include globe valves and needle valves. Although the specifics of the design differ, these two types of valves share a zig-zag or “S” shaped channel in the valve.
A stem, usually coming down vertically, introduces a stopper into the channel to completely close off the valve. When that stopper (or “needle” in the case of a needle valve) is raised, it allows fluid or gas to flow freely the opening and around the stopper itself.
As the stopper is moved farther from the valve seat, the greater the flow.
Because the design distributes the flow evenly around the stopper, there is less wear on any particular part. That means these control valves tend to have a longer life than gate valves pressed into service for the same regulatory job.
Needle valves are often used with pressure gauges where high pressure may be present, but flow rate tends to be lower. Globe valves come in much larger sizes and are used to regulate all kinds of material. Read more about global valves or needle valves.
“Check valves” are a different type of control valve. They regulate the direction that liquids and gasses flow rather than the flow rate. As we will see, it takes a certain amount of pressure to activate the check valve, making them a kind of automatic control valve.
Like many of the other valves in this article, a number of designs fall into the check valve category. However, we will be discussing two of the most common types, the swing check valve and the spring-assisted check valve.
The swing check valve relies on a swinging flap, hung vertically inside the pipe and held in place by gravity. When enough pressure is applied in one direction, the flap swings open, allowing flow to pass. Once that pressure decreases, the flap falls back into place.
If pressure is applied from the other direction, the flap is pressed firmly against the valve seat stopping backflow.
Because of the design, the swing check valve can only be installed horizontally. A spring-assisted check valve can be installed horizontally or vertically.
Available in both “in-line” and “Y-Check” varieties, the major benefit of a spring check valve is its quiet and smooth operation. The valve uses a spring loaded stopper pressed against a valve seat. When enough pressure is applied against it, the spring contracts, allowing some fluids or gas to pass.
The valve opens only enough to permit the flow needed and then closes swiftly, but because it is responding to the amount of pressure in the pipe, you do not usually have a “water hammer” effect.
The swing check valve we sell only requires 0.5 psi to open, while the spring-assisted check valve requires more pressure to be activated - as little as 1 psi or as much as 200 psi.
MAKING A DECISION
So, when deciding on a valve, take its operation into account. If you need some flow, especially if it should only ever travel in one direction, then a control valve is the way to go. If your only need is to stem the flow entirely – especially if it needs to be shut down quickly – then a shut off valve is probably the answer.
Next week, we’ll talk about the materials used in valves and their different properties.