"Sacred Sperm" was born from the worries of a religiously observant father, Ori Gruder, who did not know how to talk to his 10-year-old son about the act of masturbation or sex in general.
Filmmaker Gruder, who has six children, says he wanted to explore how ultra-Orthodox Judaism requires boys and men to go against their natural urges in the name of religion.
"For me, that is the most important issue of the film and human beings: how we cope with something that does not go according to the laws we were taught," he told Israeli newspaper Haaretz.
Gruder, 44, grew up as a secular Jew but turned to religion at 30. Using this unique perspective, his film sheds light on the specific ways Orthodox Judaism helps people fight the urge to masturbate.
In the documentary, one rabbi explains how young boys are taught to urinate without physically touching themselves, and how, from the age of 13, they wear special underwear that lets them pass water freely.
Part of the hour-long film addresses the lengths to which boys and men go to avoid getting an erection -- and how to handle it when the inevitable happens.
"They dig their fingernails into their legs, stand on their toes, do relaxation exercises," Rabbi Yisrael Aharon Yitzkovitch explains.
"Deep breathing can also help. Jumping, fast walking."
Gruder offers a rare glimpse of this sensitive subject, filming in places which are normally off-limits to the secular world: ritual baths, religious seminaries and weddings, where men and women are kept completely apart.
Mostly shot on location in Israel, where around 11 percent of the population of 8.2 million are ultra-Orthodox, the film also includes parts filmed in Ukraine where there is a 200,000-strong Jewish community.
The ban on masturbation appears to originate from a story in Genesis about a man called Onan who "spilled his seed on the ground" -- an act which the Orthodox believe cost him his life.
His name forms the root of the Hebrew word and an English synonym for masturbation, an act viewed as wicked by the ultra-Orthodox but parodied to great effect by Monty Python in the song: "Every sperm is sacred."
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In the film, Gruder asks Yitzkovitch whether he has even seen the sacred seed.
"Where am I going to see sperm? Where?" Yitzkovitch says, laughing.
Gruder in return wonders out loud: "How can you teach your child if you don't know what comes out of your body?"
But the documentary goes beyond the issue of self-love, revealing reveal a profound level of sexual ignorance among religious youngsters.
In one scene, a young man who is about to get married is seen meeting with a "sexual counsellor" whose job is to instruct him in the basics of consummation.
"Every position is allowed but our sages have a tendency to say that the best is when the man is on top of the woman, which allows for a greater union," the counsellor explains, as his client looks on blankly.
TIME TO TALK
In order to avoid exposure to the secular world, the ultra-Orthodox largely eschew going to the cinema, watching television or surfing the Internet.
However, news of Gruder's film has spread like wildfire with many downloading it online.
A recent screening of the documentary at an art-house cinema in Jerusalem was packed with secular viewers along with a handful of observant Jews.
Screenings are also planned in Britain and the US.
Gruder says he hopes the film will help to break down resistance to discussing the sensitive and complicated issue of masturbation among the Haredi community.
"It was impossible to talk about such a topic in the past. But today, Haredi teenagers can find anything by pressing a few buttons, and that changes everything," he told Haaretz.
"I believe the rabbis feel the time has come to put these subjects on the table and talk about them."