While the downside of hiring an unqualified plumber to work in you home is seldom so tragic, be aware of other pitfalls. A plumber who can’t be bothered to get a license is almost certain not to trouble himself about other forms of paperwork, like insurance. So if he manages to burn down your house, you haven’t got much chance of recovering the damages in court. (And many home insurance policies don’t cover damage caused by unqualified tradesmen.) But most of all, "these guys pretty much never guarantee their work," says O’Brian.

He’s referring to a legally binding, written guarantee; not a smiling assurance that "I’ll take good care of you." The lack of a guarantee means that if an unlicensed plumber fails to fix your problem (or makes it worse), he can tell you to go suck an egg and there’s not a thing one you can do about it.

One plumber who knows all about the kind of work that his underdocumented brethren do is Roy Van Allen, at Always Ready Plumbing (now named Allied Plumbing & Heating Corp.) "About half of our jobs are cleaning up mistakes made by guys who call themselves plumbers," says Van Allen, "but who don’t know what the hell they’re doing."

Van Allen entered the trade as a carpenter when he was 17. He was working on a construction project, "but I realized in about a week that I didn’t like it, " he recalls. "The same day I decided I wasn’t coming back, the plumber fired his assistant. He asked me if I wanted to give it a try, and I haven’t stopped since."

In the two decades since, Van Allen has earned his own plumber’s license and developed an extensive network of contacts within the New York construction trades, which enables him, if necessary, to bring in assistants who specialize in a variety of exotic disciplines. "I won’t go on a job," he says, "unless I’ve got exactly the right people backing me up, I’d rather turn down the business."

Van Allen is also a purist when it comes to guarantees. "We give you 30 days on basic repairs and a year on large contract work," he says. "Anything goes wrong in that time, it’s our problem – not yours." This kind of peace of mind will run you $59 for an evaluation of what’s wrong (that fee is waived if you hire Van Allen) and a starting rate of about $150 for basic repair work. (Van Allen charges by the job rather than the hour, and these fees generally include materials, unless the client insists on a brand of hardware he doesn’t carry.)

In a typical month, Van Allen’s work encounters run the gamut from fixing a faucet to construction contract worth half a million dollars. "There’s not too much that we can’t handle," he says with the testosterone-infused understatement that seems to be the lingua franca of all top-flight plumbers.

They can also handle it at any time. Many plumbing services that advertise 24/7 availability are pulling your leg. After normal business hours the number rings to an answering service. But Van Allen (or one of his four full-time assistants) carries a cellular phone at all times. So if water starts flooding your basement at 4 o’clock in the morning, you can reach somebody directly. "If it’s an emergency," Van Allen says, "we can usually be there in a half hour or less."