Water Gauges

What is a Water Gauge?

A water gauge is a device that allows the liquid level in a vessel to be visually inspected. Water gauges are required by the ASME Boiler and Pressure Code on steam boilers and are also useful in many other applications, such as monitoring the amount of oil in an oil tank.

Things to remember about water gauges:

Some items to keep in mind:

Pressure ratings may be influenced by limitations of the valve body, gauge glass, and gauge glass gasket. As temperatures increase, pressure ratings decrease. The larger the glass diameter and the longer the glass length, the lower the pressure rating.

Temperature ratings may also be influenced by limitations of the valve body, gauge glass, & gauge glass gasket. Use guard rods and tubular gauge glass protectors to help protect the glass from accidental breakage. Some applications require glass protectors.

Use redline gauge glass where pressures permit to allow for easy reading of the gauge. Use large diameter (3/4”) glass for increased visibility.

Use automatic ball checks to help minimize the risk of property damage or personal injury in the event of gauge glass breakage. Vertically rising automatic ball checks conforming to ASME requirements are available.

Boilers operating above 400 psig require two water gauges.

All water gauges on all steam boilers must examine the gauge glass regularly for any signs of clouding, scratching, erosion, or corrosion. The glass should be inspected daily until the need for replacement becomes apparent. This will help establish the routine inspection and routine replacement schedules.


Use commercial non-abrasive glass cleaners to keep glass clean. Use diluted acids such as hydrochloric (muriatic) acid when regular cleaners do not seem to work. Do not use wire brushes or any other abrasive materials which could scratch the glass?


Examine the surface of the glass for scratches, corrosion, chips, cracks, surface flaws, or nicks. To do this, aim a very bright concentrated light at an angle of about 45 degrees. A defective glass will glisten as the light strikes imperfections.

Glass which appears cloudy or roughened, and will not respond to cleaning, should be replaced.


Keep gauge glass in original packaging until ready to install.

Call Steam and Valve Specialists for premium water gauges for various industries. Our team will be able to find the perfect water gauge for the application.