Short answer: the state rules we checked do not ban a laundry line to the yard by name, but they do define washing machine water as sewage, and the septic rules keep effluent off the ground. Your township code is where a direct ban would be, and it varies from town to town.
People ask this a lot, usually because the drain line is already run out the back door and somebody is about to sell the house, or the septic is acting up. The honest answer has two parts, and the first part is the one most people do not expect.
The state calls your washer water sewage
The New Jersey septic code defines "sanitary sewage" at N.J.A.C. 7:9A-2.1 as the water carried wastes from water closets, laundry tubs, washing machines, sinks, dishwashers, and similar sources. Your washing machine is named in the definition. The rule does not say laundry water is a lesser kind of waste.
The same section defines greywater as the part of sanitary sewage that does not come from toilets or urinals. So laundry water is greywater, and it is still sanitary sewage. Calling it greywater does not change what it is in the eyes of the state.
The septic rule on the ground
N.J.A.C. 7:9A-1.6(d) says individual subsurface sewage disposal systems "shall not be located, designed, constructed, installed, altered, repaired or operated in a manner that will allow the discharge of an effluent onto the surface of the ground or into any water course."
That rule is written for septic systems, and it is the reason a washer line running onto the lawn is hard to defend on a septic property. If your house is on a septic system, washer water that goes to the yard instead of the tank is not treated by anything, and the rule was written to keep exactly that off the ground. If your house is on sewer, this section does not apply to you directly. Your town's sewer rules and code decide that case.
Reusing laundry water is a permit question, not a hose question
New Jersey does allow greywater reuse, but through an approved system. N.J.A.C. 7:9A-7.5 says a greywater system "may be approved by the administrative authority" if all the standards are met, and that the blackwater from the same building still needs an acceptable disposal method. A garden hose run from the washer is not an approved system.
Where the enforceable answer usually lives: your town
The state rules above are the baseline. Whether a particular yard drain breaks a rule that someone will actually enforce is usually a question for your township. Check the municipal code online, and call the township construction or zoning office or the local health department and ask directly whether laundry discharge to the yard is allowed on your property. Get the answer in writing if you are about to sell.
If the washer is draining outside because the septic cannot keep up with the load, the drain is treating the symptom. The septic is telling you something, and the fix is to find out what, not to move the water out of sight.
Common questions
Is it illegal to drain a washing machine outside in New Jersey? The state rules we checked do not name a laundry line to the yard as a violation on their own. They do define washer water as sewage, and the septic rule bars a septic system from being operated so that effluent reaches the ground surface. A direct ban, if your town has one, will be in the township code.
Is laundry water greywater, so it can go on the lawn? No. Greywater is a category inside sanitary sewage under N.J.A.C. 7:9A-2.1, not an exemption from it. Reuse for the yard needs an approved greywater system under N.J.A.C. 7:9A-7.5.
Does the septic rule apply if my house is on sewer? The surface discharge language in N.J.A.C. 7:9A-1.6(d) is written for individual septic systems. On sewer, your township's rules are the ones to check.
Can I just run the washer drain to the storm drain or the street? Do not. Nothing we checked makes that legal, and it puts sewage into a system that is not built to treat it. Ask your township before you change anything.
What should I do if the washer has been draining outside for years? Find out whether the house is on septic or sewer, then ask the township whether the outdoor discharge is allowed on your property. If the house is on septic and the outdoor line is there because the system is struggling, have the septic inspected before you add to it.
Still not sure how this applies to your property? That is what a free on-site estimate is for. Call 862-268-2510 or tell us what is going on, and we will give you a straight answer, including when the answer is that you do not need us.
