How to Choose a Solenoid Valve: 6 Checks Before You Buy

Two solenoid valves can look almost identical and perform very differently. Matching the pipe size is only the beginning: pressure, voltage, seal material, and operating function all affect whether a valve suits your equipment.

Before ordering a replacement or selecting a valve for a new application, check these six details.

1. Identify the fluid and temperature

Start with what flows through the valve. Water, air, oil, steam, and cleaning chemicals can require different body and sealing materials.

Record the fluid, its concentration where relevant, and its operating temperature. Confirm compatibility for the complete valve—including its seals—against the manufacturer’s specifications.

2. Match the connection size and thread

A 1/4-inch connection does not tell you everything. You also need the thread standard, such as NPT or BSP.

Check the equipment connection and the complete valve part number. Similar-looking threads should never be treated as interchangeable.

3. Check minimum and maximum differential pressure

Differential pressure is the difference between the valve’s inlet and outlet pressures.

For example, an inlet pressure of 5 bar and an outlet pressure of 4 bar produce a differential pressure of 1 bar.

This matters because some valve designs need a minimum differential pressure to operate. For gravity-fed systems or applications where pressures can equalize, check whether the selected valve is rated to operate at zero differential pressure.

Also verify the maximum rating for the exact valve and coil combination.

4. Confirm the electrical supply

Read the coil label and check:

• Supply voltage.
• AC or DC operation.
• Frequency, where specified for AC.
• Coil power and approved valve compatibility.
• Connector type.

A 24VAC coil and a 24VDC coil are different electrical options. Physical fit alone does not confirm that a replacement coil is suitable.

5. Choose the required operating function

For conventional, non-latching valves:

• Normally closed: closed when the coil is de-energized.
• Normally open: open when the coil is de-energized.

6. Check flow capacity and installation requirements

Connection size alone does not establish flow capacity. Compare the manufacturer’s Kv or Cv value against the required flow and allowable pressure drop.

Then check installation dimensions, flow direction, mounting requirements, environmental protection, and any certifications required for your application.

Need help identifying a replacement?

Send Hydronics Depot clear photographs of the valve body and coil label, along with the equipment make and model. Include the fluid, temperature, pressure range, connection size, and electrical supply.

Visit Hydronics Depot or email contact@hydronicsdepotinc.com for help narrowing down the options.