Melrose Park Mayor Ron Serpico is standing behind his deputy police chief amid new questions about the high-ranking cop’s moonlighting.

Several years ago, Serpico and the Melrose Park Village Board adopted a conflict-of-interest policy for village employees after revelations the deputy chief, Michael Castellan, was running a side business called Shirt Stop that sold police uniforms to underlings answering to Castellan.

Castellan’s business also had sold his own department more than a dozen Motorola radios, though he couldn’t say where the radios came from, and Motorola said he wasn’t one of its licensed dealers.

Now, Castellan has a different side job, as a plumbing contractor. On Feb. 13, a Chicago Sun-Times reporter saw him overseeing a crew fixing a leaking below-ground water pipe in a privately owned parking lot behind a North Avenue strip mall.

The name of the company Castellan initially said was handling the job is long defunct. Later, he said it was actually another company he owns. But that company isn’t registered with the Illinois Department of Public Health, as state law requires for such work. Also, records show Castellan isn’t a licensed plumber, and he acknowledges his workers aren’t, either.

Those violations can bring a fine of $1,000 or more, plus misdemeanor charges, according to state health officials, who say the rules are meant to ensure that drinking water isn’t inadvertently contaminated and infrastructure isn’t damaged by unqualified workers.

“Licensed plumbers have a minimum four-year apprenticeship,” said Justin DeWitt, chief engineer for the state public health agency. “They have experience.”

The pipe that Castellan’s workers were fixing supplies fresh water to the strip mall, whose manager called in Castellan, officials said.

Castellan said he was taking a half day off from the police department but later decided to take off the entire day.

Castellan had his police-issued sport-utility vehicle at the work site. His boss, police Director Sam Pitassi, said he doesn’t have a problem with that because Castellan is always on call for emergencies.

Melrose Park Mayor Ron Serpico. | Sun-Times files

Serpico says: “Our inquiry with appropriate village offices indicates that Mr. Castellan was not in violation of any village ordinance in connection with work on the water pipe in question.”

Castellan, who first identified his company as Diesel Ventures, which state records show is defunct, later said his company is LT MAC Enterprises.

Melrose Park building commissioner Ralph Sorce said he understood LT MAC did the excavation and a licensed plumbing firm did the pipe work.

But Castellan said his crew fixed the pipe and that he called in another firm only when there was another leak later.

Sorce said Castellan was allowed to start the project before getting, or paying for, a village permit because it was an “emergency” job to halt a leak of water that taxpayers were paying for because the hole in the pipe was short of the strip mall’s water meter.

Castellan, though, said the leak was discovered a couple of weeks earlier and the only reason he did the work that day was that it was relatively clear and warm.

Castellan’s company didn’t have an insurance bond, as Melrose Park requires, when he began the work. He got that a day later, records show, and also got the permit.

“If I did something wrong, I’m totally sorry for that,” he said. “I’m a stickler for rules.”