Acting Nassau Police Commissioner Thomas Krumpter, a 25-year veteran whose tenure as top cop included annual crime reductions even as the county’s fiscal distress resulted in closed precincts, said Monday he is retiring.

Krumpter’s retirement, after three years leading Nassau’s 2,500-member department, is effective July 20.

Krumpter, in an interview in his office Monday afternoon, said he wrestled with the decision to leave the department, calling being a cop “the only thing I ever wanted to do in life.”

He said he had accomplished many goals — historic crime lows and revamping the department’s use of force policy — but acknowledged his recent health scare and said the thought of spending more time with his family influenced his decision.

“You just know when it’s time,” said Krumpter, 50, the son of a late Nassau police sergeant. “I’ve dedicated a big chunk of my life and the truth is, over the last several years, my life has revolved around this department . . . and you miss a lot of things with your kids.”

Nassau Deputy Commissioner Patrick Ryder will become acting commissioner, County Executive Edward Mangano announced Monday.

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Ryder, a 33-year police veteran who until six months ago was a detective sergeant and the commanding officer of the department’s Asset Forfeiture and Intelligence Unit, declined an interview with Newsday, but said in a statement that becoming commissioner “is the highest honor that anyone can receive.”

Krumpter said his decision to leave now had “nothing at all” to do with Mangano, who is under federal indictment on corruption charges. Mangano has pleaded not guilty.

Krumpter’s tenure as commissioner appeared uncertain past November’s upcoming election for county executive. Mangano, a Republican, has not yet said whether he’s running for re-election, but his party has nominated State Sen. Jack Martins for the job. Nassau Legis. Laura Curran received the Democratic nomination.

Krumpter led the department “with honor and distinction,” Mangano said in a statement.

“From the fiscal constraints demanded by homeowners to balancing public safety and the war on heroin and terror, Commissioner Krumpter has streamlined back-office operations to protect taxpayers, while maintaining the number of police officers assigned to patrol and bolstering special units,” Mangano said.

Mangano said he chose Ryder to head the department because of his experience in leading the successful intelligence-led policing model.

Though Krumpter has been in talks to become the chief of the Lloyd Harbor Village Police Department, he said Monday he is juggling several job opportunities, both in government and the private sector.

“I have five different job offers right now and I haven’t told anybody,” said Krumpter, specifying three are in the private sector, one in law enforcement and another in government. He said Lloyd Harbor has not formally offered him the chief’s post.

Krumpter, who joined Nassau’s force in 1992, was named acting commissioner by Mangano in 2014 after the executive fired former Commissioner Thomas Dale for personally directing officers to arrest a witness in a politically charged election-year case.

As commissioner, Krumpter pushed a union-stalled move to usher in body cameras and championed the controversial consolidation of police precincts. He later unmerged the Fifth Precinct in Elmont and the Fourth in Hewlett to much fanfare and dropped plans to consolidate others.

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And in 2014, he fired Officer Anthony DiLeonardo, the off-duty Nassau cop who shot a retreating, unarmed cabdriver in Huntington Station after a night drinking with another officer three years earlier. But Mangano never formally nominated him to be top cop, which would have required Krumpter to face public scrutiny before the Nassau County Legislature, which votes on all commissioner-level appointments.

As acting commissioner, Krumpter was paid about $249,000 annually. The commissioner pay is set at $175,000 so Krumpter would have had to take a $74,000 pay cut if he was confirmed to the commissioner post. The gap exists because Krumpter’s current salary was negotiated through union contracts, but the top cop’s pay is set by the county executive.

Legis. Kevan Abrahams, leader of the Democratic minority in the legislature, said in a statement: “While we wish Commissioner Krumpter well and applaud him for his years of service to the Nassau community, we call upon the County Executive to keep the replacement process in choosing a new Police Commissioner . . . as open and transparent as possible.”

Nassau District Attorney Madeline Singas praised Krumpter and wished him well.

“It’s been a great privilege to work with him to keep the people of Nassau County safe,” Singas said.

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James McDermott, president of the Nassau Police Benevolent Association, the department’s union for its rank-and-file members, which has quarreled with Krumpter over a raft of policy decisions, said: “I wish Tommy and his family well in his retirement and future endeavors.”

Krumpter, a Huntington Town native, was hospitalized last month and underwent a stent procedure but has since been back to work.

Because he is taking unused vacation time, Krumpter said his last actual day on the job will be July 7.

As for the ceremonial walkout, in which fellow cops applaud a departing member as they leave their post for the last time, Krumpter said he’s declining. “I’ll sneak out the side door,” he said.

With Sandra Peddie