Over time, the Zight sight glass tube in your boiler may become clouded because of water deposits. As a result, you may not be able to gauge the water level in the boiler, leading to potential safety hazards.

If your Zight glass is cloudy and you can no longer see the water level, it’s time to replace it with a new glass tube and glass tube washers.


What You’ll Need

Before you begin the process of replacing your boiler glass tube, there are a few tools you need to have at close hand.


1.    A New Zight Glass Tube

To ensure that your new sight glass lasts as long as possible, you should purchase another Zight glass tube. Our boiler glass is high quality, durable, and crystal clear. It does not crack or shatter easily, and it comes with a higher safety factor than our competitors.


2.   Brass Nuts

If the nuts securing your current sight glass are warped or rusted, be sure to replace them with sturdy new ones from your local home improvement store.


3.   Rubber Grommets

Rubber grommets create a strong seal on either end of your new glass tube. Don’t use old ones, as they may be thin and worn and more prone to tearing apart than brand new ones.


4.   Glass Tube Washers

The washers you use for your glass tube are just as important as the tube itself. At Zight, we offer two different kinds which are highly rated for safety and quality.

The first kind of washer is called fluorine rubber, or FKM. It can withstand steam, water, and heat, is resistant to chemicals, and holds up very well under extreme pressure.

The second kind is called ethylene propylene diene monomer rubber, or EPDM. It is better suited to low-temperature environments without steam, high pressure, or chemicals.

For boilers, we recommend FKM as the most durable solution.


5.   Adjustable Wrench 

Keep an adjustable wrench at the ready so you can quickly loosen and tighten the nuts as needed.


6.   Protective Gear

Don’t forget to wear protective eye glasses and heat-resistant gloves.


How To Replace A Sight Glass Tube

Below are 7 easy steps for replacing the sight glass tube on your boiler.


1.   Turn The Boiler’s Pressure All The Way Off

Make sure the boiler is completely depressurized before you begin the process of removing the current sight glass.


2.   Turn Off The Water Valves Leading To The Sight Glass

Turn the water valves at the top and bottom of the glass tube in a clockwise direction to turn them off.


3.   Drain The Water From The Glass Tube

Slowly open the drain cock on the bottom of the glass tube by turning it counterclockwise. Use gloves in case the water is still hot. Let all of the water drain out of the tube.


4.   Remove The Sight Glass

Slowly loosen the glass tube nuts. Keep a hold on the sight glass the entire time so that it doesn’t fall to the ground and shatter.

Once the nuts are loose, slide them onto the tube. Then carefully lift the glass up and out to remove it from the connectors.


5.   Check The Connectors For Debris

Check the top and bottom connectors on the boiler for debris, including water deposits and pieces from the rubber grommets. Make sure these areas are clean before you attach the new sight glass.


6.   Install The Replacement Glass Tube

When you’re ready to install the Zight replacement glass tube, slide a nut, a Zight glass washers, and a rubber grommet onto each end of the tube, in that order. Next, insert the top end of the tube followed by the bottom end, making sure they are secure in their connectors. Next, slide the grommet, washer, and nut into place at either end of the tube and begin tightening the nut. Use your fingers first, then the adjustable wrench to secure them. Make them snug, but do not overtighten them or you risk breaking the sight glass.


7.   Turn The Sight Glass Water Valves Back On

The last step is to close the drain cock, turn the water valves back on, and check for leaks. If everything looks secure, you may repressurize the boiler.


We Have What You Need To Replace Your Boiler Glass Tube

At Zight, we sell the glass tubes and the glass tube washers you need to replace your boiler water gauge safely. Visit our online shop today to purchase these essential supplies.