It's something that members of the Gomberg family have been doing since the early 1950s: filling seltzer bottles for delivery to homes and businesses around the five boroughs and beyond.

The Brooklyn Seltzer Boys is the only seltzer bottle filling plant left in the city. There were once dozens of them.

It was started as the Gomberg Seltzer Works by company vice president Alex Gomberg's great-grandfather Moe.

Alex joined the family business in 2012, and rebranded it as Brooklyn Seltzer Boys. They added a Seltzer delivery service, an item that when it comes down to it, is pretty simple.

"We take New York City tap water, we triple filter it through a sand, charcoal and paper filter, then it gets chilled, then it gets filled with CO₂," said Gomberg.

They fill hundreds of the iconic hand-blown reusable glass bottles every day. Many of the sturdy bottles date back decades.

The company moved from their original location in Canarsie into a new space in Cypress Hills a few years ago.  It is now also home to the Brooklyn Seltzer Museum.

"This is the history of seltzer, how it became, so you can read all about that, and we have all the old machinery that we used to use," said Gomberg, who noted they will welcome school groups and others interested in the history of seltzer, inside the working plant.

Gomberg said it's all about letting everyone know they are still in business, and doing it in a lot of different ways, including selling merchandise like a kit to make the classic New York beverage, the egg cream, which includes seltzer in the recipe.

"Being the only ones left it's important that we do it, keep doing things to keep it going," said Gomberg.