In all the years I have been watching The Honeymooners, I have noticed that Norton keeps his occupation of a sewer worker a secret. In a couple of episodes, he mention that he was an underground engineer and an engineer in subterranean sanitation. In the episode where Ralph and Norton teach Mr. Marshall to play pool, Mr. Marshall asks Norton "In what capacity do you work in?" Norton answers "About 50,000 gallons a day."

Do you really think he is embarrassed to mention to people that he works in the sewer?

No I don't think so. He usually will say afterward that he works in the sewer. During "Young at Heart" he mentioned about carving your best girl's initials into your shovel while working down in the sewer. I can see where you might think that way though. It's not uncommon sometimes for some people to try to make their jobs sound fancier.