Any serious actress who throws in with an ABC sitcom these days can't pretend she has mistaken a Fred Silverman production for one of William Shakespeare. As a self-described product of "a strict, but warm and loving, Catholic upbringing," Katherine Helmond had more reason than most to keep her hands clean of ABC's raunchy new Soap. Therefore the temptation to involve herself in something so "totally opposite" to her background was, she says, compelling.

With its sledgehammer double entendres, Soap has been subjected to relentless moral and esthetic condemnation by viewers, TV critics and even prospective sponsors. It has also, unlike most of the 23 network series new this fall, become a hit.

Helmond's sculptor husband, David Christian, expresses no objections to the show's cheerfully tasteless handling of such topics as impotence, homosexuality, promiscuity, adultery, etc. One running theme does bother him, though. As the bubble-brained Jessica Tate, Katherine carries on a December-May affair with a stud tennis pro and "it's she who gets nailed," Christian complains with genuine anger, "while her husband is the philanderer of all time. If an older woman is involved with a younger man, she becomes an evil, sordid person. That really bothers me."

He needn't add that, at 44, Helmond is 10 years older than he. The two of them, however, are hardly the drooling sensualists portrayed by Soap but artists of substance who have lived together 15 years, the last seven of them married. "It seems like since the Ice Age," Helmond says. "Neither of us can remember any other life."

Christian finds their age difference "is ideal. I've been with women my age. It just seems that more interesting things are going on in the life of an older woman. Katherine is calm and controlled and has a wise approach. I have all the fire and fury of a fool. We're a perfect complement."

Helmond, in turn, credits Christian with giving her "vitality and energy and drive and foolishness." The last is one quality she needs in contending with Soap plots that often read like Screw magazine rejects. "I don't think it's lurid," she defends stoutly. "Daytime soaps go into areas—lesbianism, married nuns, a woman in love with a priest—that would not be touched in prime time. And they're super-serious. We just take real situations and exaggerate them."

Both Christian and Helmond are transplanted Texans. She was raised in Galveston in an Irish Catholic family of three sisters. Her mother was divorced when Katherine was a baby and remarried a TV repairman. After high school and regional theater in Texas, Katherine migrated at 25 to New York and off-Broadway. Her first marriage lasted two years, and she supported herself between roles with secretarial work. Next she and some friends opened a stock theater in the Catskills. "It only took four years to bankrupt ourselves," she says. "The audiences didn't want Chekhov. They wanted Under the Yum Yum Tree."

That was the play Helmond was doing in New Hampshire summer stock when she met David, a 19-year-old assistant set designer and high school dropout from Dallas, where his father was an engineer in the aerospace industry. "Usually, summer stock is the end of a relationship," Helmond cracks. "But David was not a child when I met him. He'd been out on his own some time." "The leading lady and the assistant set designer," Christian sighs. "Ah, the great love affair." He lurked around her performances until, Helmond says, "his hot looks began to make headway." Soon they moved in together.

Initially Helmond stayed legit, spending seven years in repertory including a stint with Hal Prince (who, Soap or not, still says Helmond is "a first-rate actress") and winning a 1973 Tony nomination in O'Neill's The Great God Brown. A guest role in Gunsmoke—"I've played many ladies who are knocked around and cry a lot"—led to more TV parts. After three failed pilots, Helmond took on Soap. The show has given her what she'll describe only as "good money" and positive reaction, except from her grandmother. "Before the premiere she called to ask if I would be doing anything dirty like taking off my clothes," Helmond says. "After she saw the show she called and said, 'It's all talk and no action.' "

Christian, meanwhile, reasoned that "if sets were like big sculptures, why not just do the sculptures?" A foundry apprenticeship earned him a job executing bronzes for artist Willem de Kooning, and for the next five years Christian worked in de Kooning's East Hampton studio as production head and designer. "David is a genius at carrying out other artists' ideas," says art dealer John Richardson, not without regret. "He's such a brilliant interpreter of other ideas that his own work takes second place." Thus, while Christian built a tinfoil sculpture for Salvador Dali that sold for $125,000, his own most profitable works are in the $5,000 range.

The couple finally married seven years ago—"We wanted to protect ourselves legally," she says. "We owned property and had joint bank accounts." They now rotate between her rented house in the Hollywood Hills (where Helmond stays during Soap tapings), a beach cottage on Long Island and their favorite place: a one-bedroom flat in New York's Chelsea district decorated with Christian's sculptures and charcoal drawings.

They have ruled out children because, Helmond says, "we decided we'd rather concentrate on our own lives." To that end they practice Zen Buddhism, T'ai Chi Ch'uan (a meditation-in-motion technique) and vegetarianism. Christian also recently completed an est course and while driving a truck in a rainstorm nine days later had what he describes enigmatically as "a profound experience of my relationship to the universe." Now Helmond wants to try est because "people who love each other want to share experiences."

This year Christian is taking a guilt-free vacation from sculpting by studying philosophy at the New School for Social Research. Though he admits to sometimes wondering, "What will I answer when I'm asked what I do?" Helmond says, "Money is for paying the bills and having the freedom to live with dignity. I don't care who earns it." (His real estate investments also contribute to the kitty.) They are unconcerned about the emotional hazards of her taxing production schedule with its four-month West Coast absences. "The secret of staying like lovers is to go away," Helmond says. To be on the safe side, she adds, "We have a lot of phone bills."