A. An in-unit washer-dryer is a wonderful thing, but whether it's worth breaking the rules for depends on the size of your savings account and how lucky you feel, according to our experts.

"The core problem with washer-dryer units is that the flow of water often overwhelms the limiting plumbing capacity of older buildings," says Dean M. Roberts, a real estate attorney with Norris McLaughlin & Marcus in Manhattan.

Sudsy water that routinely backs up into sinks of other apartments in your line could lead to scrutiny of your apartment and discovery of your machine.

Worse, "the machine lines can leak, causing torrents of water to flood the apartments beneath," says real estate attorney Stuart Saft of Dewey & LeBoeuf.

In the event of a flood or fire (if the dryer catches fire), you will not only be outed, but you could wind up owing thousands to your neighbors and/or the landlord, says Manhattan real estate attorney Eric Goidel of Borah Goldstein Altschuler Nahins & Goidel.

You probably won't be evicted unless you refuse to give up the machine, says Goidel.

"The fact that several other tenants may have a washer/dryer can't in and of itself justify acquiring similar equipment," he says. "Perhaps the landlord is unaware or perhaps the tenants are rent-regulated and their leases allow it."

If you're determined to go ahead anyway, it would be wise to buy a "high-efficiency"-style machine, which uses less water and soap, to reduce the risk of overwhelming your building's plumbing. Ask the plumber to suggest ways to floodproof your set-up as much possible, and only run the machine when you are at home.

Finally, depending on your situation, you may be able to ask for a "reasonable accommodation" under the Americans with Disabilities Act. Much as residents have been increasingly successful winning exceptions for pets, you might be able to persuade your landlord or a housing court judge to make an exception based on a physical disability, such as difficulty traveling to the laundry room or severe allergies, says Roberts.

Accommodations for washer-dryers are far less common than exceptions for pets, notes Roberts. And if the washing machine causes backflow into the apartments below or other plumbing problems, the possibility of a court-ordered exception is especially unlikely, he says.

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