Myth #1  Glass will crack with hot and cold water flowing into it constantly. Water seeps into the steel and eventually ruins the tank. It also cracks as the inner tank expands and contracts with heat variation.
 
Fact  This is a very believable story. It sounds so very reasonable doesn’t it? This is not the case, however. At the time of manufacture, glass lined tanks are heated to 1600+ degrees Fahrenheit. This causes the entire tank to glow red. It is then cooled as the glass is formed and bonded to the steel. The tank is then heated to 400 degrees Fahrenheit during the epoxy powder stage. Even at these extreme temperature changes, the ceramic lining will not crack. Variations of water at only 170 degrees will not even begin to affect glass. There is a 60+ year track record to verify that fact. Compare the warranty on any aluminum-tank, copper, or stainless steel water heater. Many of our glass lined tanks are still performing to this day after 27 years.
To further verify this fact, tests were made to the inner tanks, where the entire tank was twisted and compressed to 3% variations. Even with this extreme movement, the bond is too great to crack the lining. Home water heaters have been glass lined for 60 years and more. If the “Cracking Glass” myth were true, there would be major problems in the millions of homes across America today. And in fact…Glass lined water heater tanks do not expand or contract to any a measurable degree anyway. The temperatures and pressures necessary to strain carbon rolled steel is far greater than could possibly be provided without reaching several hundred degrees and pounds of pressure more than what these units operate at..
 
 
Myth #2  Glass is not as hygienic or healthy for drinking..
 
Fact  Glass is far more hygienic than any other hot liquid containment material on earth. This is why you drink hot coffee and hot tea from a ceramic mug. Hot liquids belong in ceramic containers. This is an age-old principle that is part of our everyday lives.
This was the test: in a glass bowl, a stainless steel bowl, and an aluminum bowl filled with room temperature water, a single goldfish was placed in each. Result: Aluminum fish was dead first, stainless steel second place, and the winner is… the glass bowl!
 
 
Did you know?  Glass insulates better than metal. That is why your hand would burn if you held an aluminum mug full of hot coffee.