Earl Lutz, executive secretary of the D.C. chaper of the National Association of Plumbing-Heating-Cooling Contractors, was wrongly identified in last week's real estate section as president of the group.

When you need plumbers' services, it's important to remember that they specialize within their profession the way doctors and lawyers do.

Some plumbers work only on new construction; others do primarily renovation.

Some do only "jobbing" work -- repairing faucets, toilets and sinks; others do commercial work on hotels, restaurants and office buildings. Some work on plumbing or heating systems but not air conditioning.

"The plumbing business is like anything else," says Earl Lutz, president of the District chapter of the National Association of Plumbing-Heating-Cooling Contractors and a 29-year veteran of the business. p

"They must specialize because it is a very complex business," Lutz said. "It takes a variety of equipment and skills, and it is unlikely that a plumbing contractor will do all types of jobs unless it is a very large business."

One way to begin looking for a plumber is to check with neighbors and friends. If they can't help, call the national association. Officials there will put you in touch with a local chapter that will give you names of several qualified contractors.

A local trade group, the Washington Suburban Master Plumbers Association in Rockville, will also make referrals. Membership in this organization requires licensing and bonding in accordance with Washington Suburban Sanitary Commission rules.

The Yellow Pages are another referral source; the ads go on for pages. The size of a display ad, however, is no guarantee that you are choosing a reputable company.

For example, Anthony The Family Plumber, a firm that bought a half-page ad, has been found liable by a Baltimore city circuit court for unfair and deceptive trade practices in Maryland.

The practices included answering service calls with salesmen who did not disclose that they were not plumbers; selling customers unnecessary work -- principally replacements when repairs would have been sufficient; not performing the work contracted for -- and neither informing the customers nor refunding payment, and trying to get customers to waive their three-day right to cancel contracts.

The court also found that the company used scare tactics to induce customers to sign contracts. Tactics included telling customers their furnaces would blow up or ceilings would fall in if the work were not done.

The court's decision on fines and other penalties is expected to be handed down soon. Among the options being considered by the judge are putting the company out of business or placing its management under the supervision of a court-appointed monitor.

When calling plumbers, remember to ask basic questions. Are they registered? If so, they will have registration numbers issued by their local jurisdictions. Are they insured? If not, you could end up paying for repairs or damage done in the course of their work. Maryland and Virginia require that plumbers carry liability insurance; the District of Columbia does not.

"There are shysters operating in this area who don't bother to get a license or insurance," Lutz says. "It's not unusual for customers to give them a down payment and never see them again. Or sometimes they will begin a job which they see is beyond their capability and they'll just walk out -- leaving you with a half-finished job.

"The plumbing regulations are there for a reason -- to protect the public health," Lutz added. He advises customers to be skeptical of plumbers who want to skimp on work by deviating markedly from the code. He said customers should get several estimates if the work is sizable, and should be skeptical if one firm's prices are significantly below the others'.

"If you're having a big job done, like a water heater, sink or toilet installed, tell the prospective contractor that you want to get a permit from the city or county. That way, if the person doesn't have a license, he will resist the idea. If he does, that's an indication he's not what he says he is. It scares away the cheaters," Lutz says.

"Most jurisdictions require permits for that type of work. It's for your own protection that you get one. The plumbing inspector will go over the work to make sure the proper grade of pipe is used, that the job is properly vented, etc."

Lutz points out that for some plumbing jobs, you may not need a plumber. If your problem is a clogged drain or sewer, a cleaning service might solve it.

If you are not familiar with a contractor's work, ask for a reference. No contractor should be offended if you ask to speak to other customers.

"We always remember the ones who thank us and forget the ones who got mad about something," Lutz said. "Reputable contractors are glad to provide references."

The local plumbing inspector's office, which keeps track of complaints filed against plumbers, is another source of information. You can check the contractor's record and also file any complaints you might have.

One good reason for getting a qualified plumber is that they do not come cheaply. The usual rate charged by qualified plumbing contractors -- union and nonunion -- is $30 an hour. Many plumbers also charge for travel time one way.

When the work is straightforward -- a faucet to be replaced or repaired -- you will be charged for time and material. But if you want to get rid of an antiquated sink and have a new toilet installed, the contractor may offer you a choice of a fixed contract or paying on a time-and-material basis.

A fixed contract is a flat price for the job. Plumbers base their estimates on the job's maximum possible cost. The more the plumbers come in under that cost, the more profit they make.

"When you are having a job done that requires underground work or within the wall, then a fixed contract is a good idea," Lutz said. "When we estimate a job, we figure for the worst and hope for the best." Often this type of work turns out to be more complicated than it originally appeared, and paying on a time-and-materials basis can be more expensive than having a fixed contract.

However, "If you know the contractor and the job is fairly routine, then time-and-materials is probably the best way to go," Lutz says. "People can often get away paying less that way."

If you are paying on a time-and-materials basis, be sure your agreement includes a "not to exceed" clause.

Before work begins, ask the contractor to give you a written estimate. This is not necessarily an itemized bill for every nut and bolt, but a list of major supplies to be used and work to be done. This gives you something to use if disagreements or questions arise later. It also provides you with a record that can be useful if you decide to sell.

Lutz suggests that customers establish a steady business relationship with a plumbing firm. Firms usually provide faster service for regular customers, and service can be more effective because the plumber is familiar with your house or apartment.

If an emergency arises before you've found a plumber, remember that larger contractors are more likely to respond to your weekend or late-night call for help. They have more employes and therefore are usually better able to handle off-hour jobs.

Lutz says it is well worth a customer's time to "be careful" when choosing a plumber.

"Trying to settle a dispute that could have been avoided is often expensive" in terms of time and money, he says.