Best Seller [Lifetime Warranty] 4040 Humidifier Solenoid Valve 24V Water Valve
4040 humidifier 24V solenoid water valve with brass fittings and yellow lead wires on a mounting bracket.
4040 humidifier 24V water solenoid valve with mounting bracket and wiring for Aprilaire whole house humidifiers.
Dimensional diagram of 4040 humidifier 24V solenoid water valve showing technical specifications and measurements.
4040 humidifier 24V water solenoid valve with yellow wire for precise water flow control.
Collage showing high-grade material features of a 4040 humidifier 24V solenoid water valve.
4040 Humidifier 24V solenoid water valve with mounting bracket and yellow electrical leads.
4040 humidifier solenoid water valve with close-up view of the water inlet indication arrow.
Comparison graphic showing a durable 4040 humidifier 24V solenoid water valve versus a low-quality alternative.
4040 humidifier 24V solenoid water valve with mounting bracket and yellow electrical wires.
4040 humidifier 24V solenoid water valve with brass fittings and yellow lead wires on a mounting bracket.
4040 humidifier 24V water solenoid valve with mounting bracket and wiring for Aprilaire whole house humidifiers.
Dimensional diagram of 4040 humidifier 24V solenoid water valve showing technical specifications and measurements.
4040 humidifier 24V water solenoid valve with yellow wire for precise water flow control.
Collage showing high-grade material features of a 4040 humidifier 24V solenoid water valve.
4040 Humidifier 24V solenoid water valve with mounting bracket and yellow electrical leads.
4040 humidifier solenoid water valve with close-up view of the water inlet indication arrow.
Comparison graphic showing a durable 4040 humidifier 24V solenoid water valve versus a low-quality alternative.
4040 humidifier 24V solenoid water valve with mounting bracket and yellow electrical wires.
Lifetime Warranty

[Lifetime Warranty] 4040 Humidifier Solenoid Valve 24V Water Valve

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4040 Humidifier Solenoid Valve 24V Water Valve

Key Features

  • Controls water flow for whole-house humidifiers
  • Operating Voltage: 24V AC
  • Includes in-line strainer, compression sleeve, and nut

Replaces / Cross-Reference Part Numbers

  • AprilAire: 4040
  • Ranco: 4040-001

Compatibility & Fitment

  • Designed for AprilAire Whole-House Humidifiers.
  • Compatible Models: 220, 224, 400, 400M, 440, 448, 500, 500M, 550, 550A, 558, 560, 600, 600M, 700

When to Replace

  • Humidifier does not receive water when operating.
  • Water flow is weak, inconsistent, or stops completely during a cycle.
  • Inability to maintain set humidity levels.
  • Visible water leaks, drips, or corrosion on the existing valve body.
  • Valve makes a buzzing noise but does not open to allow water flow.

Installation Tips

  • Before installation, shut off the water supply and disconnect power to the furnace and humidifier.
  • Note the water flow direction indicated on the original valve body and install the new valve in the same orientation.
  • Use two wrenches during removal and installation to avoid twisting or damaging water lines.
  • Ensure the included strainer is correctly seated to prevent debris from clogging the valve.
  • After installation, slowly turn the water supply on and check all connections for leaks before restoring power.

FAQ

This 24V water solenoid valve is commonly used with many AprilAire whole-house humidifiers, including models 220, 224, 400, 400M, 440, 448, 500, 500M, 550, 550A, 558, 560, 560A, 568, 600, 600M, 700, 700M, 760, 760A, 768, 900, 950, and 1000. Some sources also note exclusions or model-specific differences, so the safest match is to verify your humidifier model number and compare the installed valve and part number before ordering.
The main replacement number is 4040. Cross-referenced numbers found for this valve family include 4040-001, B2015-S85, B2017-S85, A2012-S118, and 100006735. Matching both the part number and your humidifier model is the best way to confirm fit.
The solenoid valve controls water flow into the humidifier. When the humidifier calls for moisture, the 24-volt coil opens the valve and allows water to feed the unit. If the valve does not open correctly, the humidifier may run but produce little or no humidity.
Typical symptoms include no water entering the humidifier, weak or inconsistent water flow during a call for humidity, the unit operating without adding moisture, or a valve that hums but does not open. In some cases, restricted flow is caused by debris in the inlet strainer rather than a failed coil, so both the valve and strainer should be inspected.
For most whole-house humidifiers, this is usually a moderate repair that takes about 20 to 45 minutes. Basic tools often include a screwdriver, adjustable wrench or open-end wrenches, and possibly pliers. Shut off power to the humidifier and close the water supply before starting. After installation, restore water and power, then check carefully for leaks and confirm that the valve opens during a humidity call.
Before replacing the valve, verify that the humidifier is actually sending 24V to the solenoid during operation. Also check for a clogged inlet strainer, blocked feed tube, saddle valve restrictions, mineral buildup, or a plugged water panel. If the valve is receiving the correct 24-volt signal but still will not open or flow remains poor after cleaning the strainer, replacement is usually warranted.