Manual Override on Solenoid Valves: What It Is and When to Specify One
A manual override lets you open (or in some cases close) a solenoid valve by hand, without energising the coil. It is one of the most useful — and most frequently overlooked — options when specifying a valve. If your process has to keep running during a power cut, or a commissioning engineer needs to prove flow before the control panel is wired, an override can save hours of downtime. This guide explains how overrides work, the main types, and how to decide whether you need one.
Why fit a manual override?
A standard solenoid valve only changes state when its coil is energised or de-energised. That is fine in normal running, but there are several situations where operating the valve by hand is invaluable:
Commissioning and testing. During installation you can confirm flow, fill a line, or bleed air before the electrical control system is live. This is often the single biggest reason engineers ask for an override.
Power failure. On a normally closed valve, a mains failure shuts the valve. An override lets an operator open the line manually to keep a critical process going, drain a tank, or maintain cooling until power returns.
Maintenance and fault finding. Being able to actuate the valve mechanically helps you separate a mechanical problem (stuck plunger, blocked orifice) from an electrical one (failed coil, wiring fault) without a multimeter in hand.
The two main types of manual override
Overrides fall into two broad families, and the difference matters a great deal in practice.
A momentary (non-latching) override — usually a small push-pin or push button — opens the valve only while you hold it. Release it and the valve returns to its normal state. This is the safer default, because the valve cannot be accidentally left open.
A maintained (latching) override — typically a screw or push-and-turn actuator — holds the valve open until you deliberately return it. This is what you want for extended manual running, but it introduces a real risk: if an operator forgets to reset it, the control system will appear to be in command while the valve is mechanically locked open.
| Feature | Momentary (push) | Maintained (screw / push-turn) |
|---|---|---|
| Holds position when released | No | Yes |
| Best for | Quick tests, bleeding, proving flow | Extended manual running during power loss |
| Risk of being left engaged | Very low | Higher — must be reset by hand |
| Typical actuation | Press and hold | Turn or push and lock |
Override versus latching valve — not the same thing
It is easy to confuse a manual override with a latching (bistable) valve, but they solve different problems. A latching valve uses a brief electrical pulse to change state and then holds that state with no continuous power — it is an electrical energy-saving feature. A manual override is a mechanical hand control that works with no power at all. If your aim is to reduce coil power consumption, look at a latching solenoid valve; if your aim is to operate the valve by hand during commissioning or a power cut, you want an override. Some valves can offer both.
How valve type affects the override
The way a valve works changes what an override can practically do. On a direct-acting valve, the override typically lifts the plunger straight off the seat, so it operates reliably from zero pressure differential — ideal for gravity-fed or low-pressure lines. On a pilot-operated (servo-assisted) valve, the override usually opens the pilot passage, which means it still relies on a minimum differential pressure across the valve to lift the main diaphragm. If there is little or no pressure difference, a pilot valve may not fully open even with the override engaged, so it is worth checking this against your line conditions before ordering.
Safety and hazardous-area considerations
An override is a deliberate way to defeat the automatic control of the valve, so it should be treated as part of your safety assessment. On any interlocked or safety-related circuit, consider whether a maintained override could leave the plant in an unsafe state, and label overrides clearly so operators know a valve is being held open by hand. In potentially explosive atmospheres, the override must not compromise the enclosure's protection concept — ATEX-certified solenoid valves are available with compliant override options, and you should never fit a non-certified override to a valve destined for a hazardous area.
How to specify the right override
When you request a quotation, be explicit about four things: whether you need momentary or maintained action; whether the valve is direct-acting or pilot-operated; the line pressure conditions the override must work against; and any certification requirements such as ATEX or IP ingress rating. Getting these clear up front avoids the common disappointment of an override that will not open a pilot valve at low pressure, or a maintained override on a safety circuit where a momentary one was really needed.
If you are still weighing up the wider specification — body material, seal choice, port size and coil voltage — our guide to choosing a solenoid valve walks through the full decision, and the Valve Search Wizard helps you shortlist products by application. If you are unsure whether an override is right for your process, or which type to fit, the FAQ covers common questions and our team is happy to check the details before you order.