A solenoid valve is an electrically operated valve that opens or closes on its own the moment an electric current energizes a coil, controlling the flow of liquids or gases through a system without anyone touching a handle. Send the coil power and the valve switches. Cut the power and it switches back. That simple, automatic on/off control is what keeps pools filling, car washes spraying, water treatment systems running, and countless production lines moving.
For engineers, OEMs, and purchasing teams, the real question is usually not just what a solenoid valve is. It is which one belongs in your system, and what happens if you get it wrong. A delayed or mismatched valve does not just slow a project down. It can shut an operation down. This guide walks through how solenoid valves work, the main types, where they are used, and the handful of specifications that decide whether a valve performs for years or fails when you can least afford it.
What Is a Solenoid Valve, in Plain Terms
A solenoid valve combines two parts working together: a valve body that the fluid passes through, and a solenoid, which is an electromagnetic coil mounted on the valve. The valve body does the mechanical work of opening and closing a flow path. The solenoid provides the muscle, converting electrical energy into the motion that moves the valve open or shut. Put simply, what a solenoid valve does is give a control system electrical, on-demand command over flow, which is why it is also called an electrically actuated valve.
Because the switching is electrical, a solenoid valve can be controlled remotely, automated on a timer or sensor, and cycled thousands of times without manual effort. That makes it one of the most common flow-control components in industrial and OEM equipment. Anywhere a system needs to start, stop, or redirect a fluid reliably and on command, a solenoid valve is usually doing the job.
The fluids involved vary widely. Water, compressed air and other gases, light oils, and mild corrosive media all run through solenoid valves every day. The right valve for each depends on the media, the temperature, the pressure, and the flow, which is exactly where valve selection begins.
How Does a Solenoid Valve Work?
The working principle comes from electromagnetism. A solenoid is a coil of wire that produces a magnetic field when current flows through it. As Encyclopaedia Britannica describes it, a solenoid is an electromechanical device that produces mechanical motion when energized with an electric current, using a cylindrical plunger that moves inside the coil. When the coil is energized, the plunger is pulled by magnetic attraction. When the current stops, a spring returns it to its resting position.
In a solenoid valve, that moving plunger opens or closes the flow path. Energize the coil and the plunger lifts a seal off its seat, or drops it onto the seat, depending on the design, changing whether fluid can pass. The whole action takes a fraction of a second. The term solenoid was coined by André-Marie Ampère in 1823, but the modern solenoid valve applies that same principle to fluid control.
Two behaviors are worth understanding before you specify anything, because they determine how your system fails safe.
Normally Closed vs. Normally Open
A normally closed valve stays shut when there is no power and opens only when the coil is energized. A normally open valve does the opposite. It stays open without power and closes when energized. The choice is not cosmetic, because it decides what your system does during a power loss. If you want flow to stop the instant power is cut, you choose normally closed. If flow must continue during an outage, you choose normally open. Getting this backward can turn a simple power blip into a flooded floor or a stalled process.
Direct-Acting vs. Pilot-Operated
Direct-acting valves use the solenoid to move the seal directly, so they work even at zero pressure. Pilot-operated valves, often built around a flexible diaphragm, use the pressure of the fluid itself, with the solenoid controlling a small pilot port that does the heavy lifting. Pilot-operated designs handle higher flows efficiently, but they usually need a minimum pressure differential to function. If your system runs at low or no pressure, a direct-acting or specialty zero-pressure valve is the safer choice. This single distinction is one of the most frequent reasons a valve underperforms in the field.
Common Types of Solenoid Valves
Beyond how they actuate, solenoid valves are grouped in a few practical ways.
2-Way and 3-Way Valves
A 2-way valve is the simplest design: one inlet, one outlet, and a single flow path it either opens or closes. A 3-way valve has three ports and can switch flow between two paths, which is useful for diverting, mixing, or venting. Most basic on/off jobs use a 2-way valve, while applications that need to redirect flow reach for a 3-way.
Low-, Medium-, and High-Flow Valves
Valves are also sized by how much fluid they need to pass. Low-flow valves handle small, precise volumes, medium-flow valves cover the broad middle of most applications, and high-flow valves move large volumes through bigger lines. Industrial Plastic Valves builds its line in body sizes from 1/8 inch to 3 inches to cover that full range, along with specialty valves for zero-pressure and other demanding conditions.
What Are Solenoid Valves Used For?
The range of systems that rely on solenoid valves is broad, spanning consumer-facing water systems and heavy industrial equipment alike. Common applications include:
- Swimming pools, spas, and hot tubs, where valves manage filling, circulation, and filtration.
- Decorative and memorial fountains, splash pads, and aqua parks, where timed water effects depend on fast, repeatable switching.
- Vehicle and car wash systems, where valves control the precise sequencing of water, soaps, and rinses.
- Water filtration and treatment systems, where reliable shutoff protects both the equipment and the water supply.
- Water bottle refill stations and drinking fountains, where compact valves dispense on demand.
- Industrial and OEM equipment, where solenoid valves are built into machinery to automate compressed air, water, and light-oil flow.
The common thread is that these are systems where downtime is expensive and a stuck or failed valve is felt immediately. That is why the application matters as much as the valve itself when you choose materials and configuration.
Choosing the Right Solenoid Valve: What Actually Matters
This is where understanding what a solenoid valve is turns into specifying the right one. Four decisions carry most of the weight.
Body Material
The body has to be compatible with the media flowing through it and with the temperature of that media. Each material has a working range:
- PVC offers excellent resistance to acids, alkalis, salts, and oils at low cost, with a maximum fluid temperature around 120°F.
- Noryl GTX is a rigid thermoplastic blend with strong chemical resistance to fuels, oils, and alkaline chemicals, rated to roughly 300°F.
- Polypropylene provides superior solvent resistance and light weight, with a maximum around 180°F.
- Brass and stainless steel are metal bodies suited to higher pressures, temperatures, and mechanical demands.
Matching the body to your media is the difference between a valve that lasts and one that degrades early.
Seal Material
The elastomer seals inside the valve are just as critical for chemical compatibility:
- Buna-N has excellent abrasion and tear resistance and suits water, oils, and petroleum fluids, with a range of about 20°F to 180°F.
- EPDM handles many acids, alcohols, and oxidizing chemicals, but not petroleum-based fluids, and is rated roughly 20°F to 250°F.
- Viton offers broad chemical compatibility for acids, hydrocarbons, fuels, and solvents that would swell Buna-N, with a range near 10°F to 300°F.
A valve can have the perfect body and still fail early if the seal is wrong for the fluid.
Size, Flow, and Configuration
Finally, the valve has to match the physical demands of the system. That means the right port size and flow capacity for your required volume, the correct solenoid voltage, and the wiring configuration your controls expect. Get these right and the valve drops into the system and performs as specified.
If you are weighing these choices for a specific system, you do not have to guess. The team at Industrial Plastic Valves will help you pin down the right material, size, and configuration for your media before you order. Call or text (775) 883-6108 and talk to someone who knows valves.
Why the Right Valve Matters
On its own, a solenoid valve is small and inexpensive, which is precisely why a poor choice is so disproportionately costly. Catching a specification problem during selection costs a phone call. Catching it after installation costs downtime, rework, and a system offline while the correct valve is sourced. That imbalance, not the price of the valve, is what makes careful selection worth the few minutes it takes.
Frequently Asked Questions
Are solenoid valves AC or DC?
They can be either. Solenoid valves are available with coils wound for different voltages, commonly 12V and 24V DC for battery, sensor, and control-panel systems, and 120V or 240V AC for line-powered equipment. The coil voltage has to match your power supply, so it is one of the first details to confirm when ordering. Industrial Plastic Valves offers multiple voltage options across its line.
How long does a solenoid valve last?
Service life depends heavily on duty cycle, media cleanliness, and whether the valve is correctly matched to the application. A valve built for continuous-duty operation and specified with compatible materials can run reliably for years. The fastest ways to shorten a valve’s life are running incompatible media through it or exceeding its temperature rating, which is why material selection matters so much.
Can a solenoid valve be repaired, or does it need to be replaced?
Many solenoid valve problems come from a worn seal, a stuck plunger, or debris on the seat, and those can sometimes be cleaned or rebuilt with a repair kit. A burned-out coil or a cracked body, on the other hand, usually calls for replacement. If a valve fails repeatedly, that is often a sign it was mismatched to the application in the first place, and a better-suited valve will outlast the repairs.
Does a solenoid valve need to be installed in a particular orientation?
Most solenoid valves are designed to be mounted with the coil upright, above the valve body, and with flow following the direction marked on the valve. Installing a valve backward or upside down can cause it to stick, leak, or fail to seal. Always check the flow arrow and the orientation guidance before mounting, especially on pilot-operated valves that rely on gravity and pressure to seat correctly.
Get the Right Valve, Right Now
You should not have to source parts, test configurations, and hope a valve works. For more than 35 years, Industrial Plastic Valves has helped engineers, OEMs, and purchasing teams get the right valve the first time, with no minimum order quantities and real people on the phone to talk it through.
If you know your application but want to confirm the right fit, or you are not sure where to start, reach out to the team. Call or text (775) 883-6108, or send your specs by email and get a clear answer. Get the right valve, right now, so your system keeps moving and your project stays on track.