It’s the $500,000 drip. And it has a Brooklyn homeowner desperately fighting City Hall.

East Flatbush resident Joseph Sparrow was assessed a jaw-dropping $552,483 in total water charges and penalties by the NYC Department of Environmental Protection over a four-year period, according to documents reviewed by The Post.

“This bill amount is totally impossible — someone said I would have had to be running a fire hydrant around the clock to run up anything close to what the city has billed me,” Sparrow, 28, told The Post.

“We have tried to reason and talk with the water department,” he added, “but they are nasty and difficult about this, saying I owe the money.”

Four years ago, Sparrow’s water supply was shut off, helping curb his astronomical bills from escalating further. Yet it hasn’t stopped his nightmare.

And despite the homeowner’s protests to the water department and independent analysis by professional plumbers claiming he could only possibly have ever used about $40 worth of water monthly for his typical-size home, the city claims he owes them a lottery-size check.

The owner even paid a crew $30,000 to rip up his property to check out the plumbing for possible leaks. None was detected. And there is no evidence of a broken water meter, despite city correspondence saying otherwise, according to Sparrow.

However, city Department of Environmental Protection officials told The Post last week, “The property had a substantial water leak, which, despite several notices over the years, the owner has refused to repair, and the water bill has not been paid since 2013.”

Sparrow paid for the house in cash about nine years ago, from the proceeds of a legal settlement following his mother’s untimely death only two months after Sparrow was born. And while the settlement seemingly left Sparrow comfortable, it was also the start of his own house of horrors.

Brian Walton, CEO of Merit Holdings Group in New York, who has forensically examined Sparrow’s water bills, is stunned.

Walton notes that according to the records, there were 156,100 cubic feet of water consumed by Sparrow’s residence for which the city is seeking payment.

“I have a hard time believing there is a break in the piping, as the neighborhood would likely be flooded as a symptom,” Walton said. The neighborhood has not reported flooding during the billing period.

“To put this volume of water in context,” added Walton, “an Olympic pool contains approximately 88,000 cubic feet of water. Mr. Sparrow is being billed for, and supposedly [was] consuming, just shy of two times that amount on a monthly basis.”

Walton asserts that basic logic would indicate that the house’s problem is not Sparrow’s but related to a faulty meter, “or there is a breakage in the water main that feeds Mr. Sparrow’s residence.”

Sparrow’s attempts to put his three-bedroom house up for sale and to pay off this tab have fallen flat.

Built in 1949, the house is believed to have a market value in excess of $320,000. Since the property has no running water — Sparrow has to shower and cook at a house four miles away — he is unable to open it up for renters and some extra income. Sparrow does not work and is filing for disability due to the onset of epileptic seizures, he says.

The property, meanwhile, has been slapped with liens, and Sparrow is facing eviction in foreclosure because of these unpaid taxes.

“The foreclosure of this property tax is valid,” according to John Zandi, an accountant for Sparrow who is also defending his innocence at City Hall. “However, the judge originally did not allow for Joseph Sparrow to sell his property in a private sale because counsel/lawyers for the lien companies objected — stating that Joseph Sparrow has hundreds of thousands of dollars of water liens.”

Zandi added: “The lawyer appointed for Joseph Sparrow argued that the thousands of dollars in water liens was under dispute.”

The drama is wearing Sparrow down.

“I bought this house at 19, and I have always tried to do the right thing in my life,” he said. “This is the only thing I have, and they are trying to take it from me. I could end up homeless, living in a shelter, or with nowhere to go, if this is not resolved fairly.”