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Why You Should Vent a Liquid-Filled Pressure Gauge

liquid filled pressure gauge

Venting of the enclosure should be done immediately after installation to maintain the accuracy of full-scale liquid-filled gauges ranges of 300 psi or less, including vacuum and compound ranges of 30″ Hg0300 psi or less.

Ventilation of the enclosure may also be required at regular intervals, depending on the process. With proper venting, the liquid gauge would display accurate results. Liquid-filled gauges must be vented after installation so that the liquid doesn’t leak out during transportation.

Temperature changes during shipping and during process application often cause the filling liquid to expand and contract. These expansions and contractions change the pressure inside the sealed gauge case, which can reduce the device’s accuracy. Sometimes, the pointer may return precisely to zero once the gauge is vented to match local atmospheric pressure.

What is a Liquid-Filled Pressure Gauge?

A pressure gauge is a measuring device used to calculate the force applied by a liquid or gas on a surface.

A liquid-filled pressure gauge is filled with a liquid, such as silicon or glycerine to improve its performance in less-than-ideal conditions. Fluid can be seen because the dipstick is not filled, creating an air bubble at the top of the dipstick. Pressure gauges are widely used in domestic, commercial, and industrial applications. They provide a quick indication of pressure in a system for equipment installation, configuration, and operation.

Benefits of Liquid-Filled Pressure Gauge



Easy to read. The indicator stabilized against vibrations and pulsations.


Wear & Tear

Liquid lubrication and reduced movement frequency of gears and links result in less wear.


Temperature protection

Protected against high-temperature and extreme temperature fluctuations.


Condensation buildup is not possible.


Corrosive resistance

It is sealed, therefore, resistant to highly corrosive chemical processes such as acids and salt production.


More expensive, long-term savings


Performance in the harshest conditions

Consistent performance in all conditions.

Performance in sub-zero environment

  Protected against sub-zero conditions (up to -40°C)

Indicator speed


Slower gauge speed due to liquid resistance.

Liquid-filled gauges offer unique vibration and shock protection and are preferred in process environments with higher physical demands. Keeping a few facts in mind when selecting and installing liquid-filled pressure gauges is essential.

How to properly vent a liquid-filled pressure gauge?

Before grabbing your scissors, it’s good to know that there are two different styles of fill plugs. So the first thing to do is to determine which fill plug has been supplied with your gauge.

Solid Rubber Type

To correctly vent the solid rubber fill plugs, cut off the tip, which will open a small hole so the gauge can vent. The solid rubber-type plugs do not allow for the closing of the vent for the use of the gauge in a non-upright position. These are the most common fill plugs, as most applications don’t require horizontal installations.

Lever Type

The levers on this pressure gauge are closed on delivery and must be opened during installation to prevent any possible pressure buildup in the case. The lever is a half-turn valve used to vent the gauge by moving the valve to the open position. This allows the pressure gauge to breathe, releasing any pressure or vacuum built inside the case. The lever can be left open if the gauge is installed upright.

The lever style does allow for the use of the gauge in a non-upright position. This can be done by moving the valve to the closed position to prevent fluid leaks. However, this configuration can lead to inaccuracies if the temperature fluctuates.

Please note: The valve lever can remain open if the gauge is installed upright (no periodic venting required). However, suppose you must mount the gauge in a non-upright position. Periodic venting is recommended. During periodic ventilation, small amounts of liquid may escape due to the pressure built up inside the case.

How Do You Know You Vent Correctly?

A sign to look for to confirm that your liquid-filled pressure gauge with the solid rubber filler cap is vented correctly is to make sure that the glycerin comes out of the pressure gauge after cutting the filler cap with scissors.  

If glycerine doesn’t spill out, you can take a paper clip or a small tool and insert it into the hole of the fill plug. You can then see if the glycerin is at the end of your tool when you take it out. If you see glycerin, your fluid-filled gauge is adequately vented.

On the other hand, if you don’t see glycerine after the initial cut, you may not have snipped far down enough.

If you have a liquid-filled gauge with the lever-type fill plug, move the yellow valve to the open position. A reminder that these steps must take place after installation.

Although installing a liquid-filled pressure gauge seems easy, it can lead to issues that would cost you time and money if not properly educated. Contact [email protected], or visit our website at to learn more about how reliable liquid-filled gauges can save you time and money.

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