Owning an East End estate isn’t all it’s cracked up to be.

Hamptons homeowners say that their summers are being ruined by outrageously demanding house­guests who treat their manses like luxury hotels.

“One bachelor had sex in my hot tub with a girl he had met that night,” said novelist Holly Peterson. “He left her wet bikini on the counter. Don’t even start with me about my Jacuzzi needing fumigation after the weekends. There are so many people peeing and having sex.”

Peterson, who has been hosting 16 to 20 people at her Water Mill home for the past 20 years, said it can become a hostage situation — with weekenders treating her like a concierge, chef, towel service and taxicab rolled into one.

And while most of her friends are well behaved, she acknowledges that not everyone appreciates how much work goes into running a house.

“People are entitled. They like pick-up and drop-off at the Jitney. They want reservations at these bougie, horrible beach restaurants that you can’t even get into on a Tuesday night — and they want to go on the weekend,” she said.

“They want you to take them to Sunset Beach, which has been taken over by Russian oligarchs. They say, ‘Can you get me into Exhale?’ ‘Can you get me into Soulcycle?’ ‘Can you get me a surf lesson?’ They linger around the kitchen wondering where lunch is and what fun I am planning. They want to know what car they can borrow, what surfboard they can borrow, what racquet they can borrow. It’s exhausting.”

Peterson isn’t alone.

“It’s an epidemic,” said Susan Moss, a divorce attorney who owns a home in Westhampton. “People just show up. Someone copied my keys the last time they visited — and just showed up one weekend. I must have said, ‘Come back anytime’ and they took it literally.”

Interior design­er John Barman had a similar surprise when two women he had briefly met at a friend’s birthday showed up at his Sagaponack house with overnight bags.

“We offered them a glass of rosé and asked where they were staying, and they didn’t know,” said model Kylie Vonnahme, who was at the house and had also been at the birthday celebration. “They eavesdropped on us at dinner and thought that they would show up and hope that we invited them to stay.”

“Real Housewives of New York” star Barbara Kavovit — the author of “Heels of Steel: A Novel about the Queen of New York Construction” — spent years hosting in her six-bedroom Wainscott home. (This season it was on the rental market for $130,000 for the summer). She says the mooching starts long before guests arrive.

“There are people that you don’t hear from until about three weeks before Memorial Day hits,” says Kavovit. “Suddenly it’s, ‘Hey girl, how have you been? I haven’t seen you in such a long time and I’d love to come to your place for the weekend.’ In my head I am saying, ‘These people have a lot of cojones . . .’ But I usually just say, ‘OK, sure come out.’ ”

Peterson, likewise, has too much decorum to confront overly needy guests — saying it’s just easier to “have a glass of rosé and move on.” Nonetheless, she admitted she has banned a “couple dozen” people.

“If someone has a new person they’ve been with overnight . . . and I am getting the heebie-jeebies because they are a foreign prostitute or some disgusting lecherous guy, I get upset,” said Peterson, author of the novel “It’s Hot in the Hamptons.”

“I also don’t like children who terrorize my children and people who get inappropriately inebriated and become annoying,” she added. “I ­really hate when people smoke weed in my house.”

Kavovit explained she won’t let a few rotten apples ruin her good time because “I love to entertain. I love having a chef and being able to give people any kind of food they want at any given moment.”

But it drives her crazy when guests are cheap.

“I asked a guest to go to the store to get a bunch of bagels and they asked me for money,” Kavovit recalled, estimating the purchase cost $25.

“Another time I asked somebody to go buy tuna fish and they asked me for $8. I gave them the money but I never asked them back. It’s unbelievable how cheap people can be, especially considering what it costs to run a home.”

Owning a home in the Hamptons can leave you feeling used, she ­lamented. But worst of all, it complicates your love life.

“You have to be careful,” Kavovit says. “You have to ask yourself if they are dating you just because you have a house in the Hamptons. It’s happened to me.”