The Chicago River Dyeing Tradition Dates Back Nearly 70 Years. But How Do They Do It?

It's a famed Chicago tradition that dates back nearly 70 years and draws attention from across the country: the dyeing of the Chicago river green in honor of St. Patrick's Day.

But it's also one that comes with lots of questions: What's in the dye? How do they do it? And who does the green river dyeing honors each year?

Don't be fooled, of course -- it's not Leprechauns, or at least, not entirely. Instead, it's those who often deal with a different kind of treasure, usually found in water, rather than at the end of the rainbow: Plumbers.

The Chicago Plumbers Union, Chicago Journeymen Plumbers Local 130, says its been dyeing the Chicago River green in honor of the city's St. Patrick's Day celebrations for nearly 68 years.

And the specific green color, the union says is "identical to the greens of Ireland from where it got its name, The Emerald Isle."

Why Do They Dye the River Green?

The story goes, in 1961, a man by the name of Stephen Bailey -- the business manager of the plumbers union -- was approached by "one of his plumbers who was wearing some white coveralls," a post by Local 130 says. It was then the union says, that Bailey noticed the overalls had been stained or dyed with "a perfect shade of green," or "an Irish green to better describe it."

When wondering how the coveralls could have turned such a tint, the tale continues, Bailey and his plumbers discovered that it was from to the dye used to detect leaks in the river.

"That's when Mr. Bailey bellowed," the Union declares, "Call the mayor ... we will dye the Chicago River green!"

And there you have it.

How Do They Dye it Green?

Now, each year around St. Patricks' Day, members of the Chicago Plumbers union embark on boats that putter across the Chicago River, with a rather curious concoction that sprays dye out of plumping pipes and spout pumps.

But the mysterious mixture doesn't come out green.

"If you were watching this for the first time you would think this is a mistake or a bad joke," the post goes on to say. "You see the dye is orange, and its initial color on the surface of the river is orange, and you would think to yourself what 'heathen would do something like this.'"

However, once the dye sets in, the color in a stroke of luck changes to green, and the "true color magically appears," the union says.

WATCH: Behind the Scenes: Creating Chicago's Iconic Green River Dye

According to Local 130, other cities have attempted similar feats, but never found success. It's that, the union says, and the magical color transformation that perhaps plumbers may have had some additional help with.

"We believe that's where the Leprechaun comes in," Local 130 says.

"As the late Stephen Bailey has said, the road from Chicago to Ireland is marked in green," the post regales. "From the Chicago River to the Illinois River, then to the Mississippi, up the Gulf Stream and across the Atlantic you can see the beautiful green enter the Irish Sea, clearly marking the way from Chicago to Ireland."

What's in the Dye?

We'll never know.

The plumbers union, Choose Chicago says, "still holds the river-dyeing honors today." But you won't be able to find their recipe anywhere. "Their environmentally friendly dye formula remains a closely kept secret," Choose Chicago says.

When is the 2023 Chicago River Dyeing?

While the river dyeing begins at 10 a.m., you may want to get to the river, between Columbus and State by 9 a.m. to get your spot. 

According to the plumbers union, the best views can be found on Upper Wacker Drive between Columbus and Fairbanks.

MORE: What to Know for Getting to and From the Chicago River Dye This Weekend

If you plan to celebrate at home, you can still watch the big event, as NBC 5 will also stream it live.

Chicago St. Patrick's Day Parade

While the city of Chicago's St. Patrick's Day parade takes place Saturday, a handful of other parades and events are taking place this weekend. Here's a breakdown:

South Side Irish Parade:

• When: March 12, 2023, from 12-3 p.m.
• Where: 103rd & Western Ave. to 115th & Western Ave.

Northwest Side Irish Parade:

• When: March 12, 2023, at 12 p.m.
• Where: Neola Avenue to Northwest Highway

Chicago St. Patrick's Day Parade:

• When: March 11, 2023, at 12:30 p.m.
• Where: Columbus Drive between Balbo Drive and Monroe Drive

St. Patrick's Fest:

• When: March 11, 2023, from 1-11 p.m.
• Where: Irish American Heritage Center

Shamrock'n The Block:

• When: March 11, 2023, from 11:30 a.m.- 5:30 p.m.
• Where: Old St. Patrick's Church