Everything You Need To Know About Laundry Room Plumbing Codes

Not every house has a laundry room. In mine, we keep the washing machine and dryer in the main bathroom. In some homes, these appliances live in a corner of the basement.

Older homes are the ones most likely to lack a laundry room. Most contemporary homes have one in the basement, on the ground floor, and sometimes on the second floor.

In laundry rooms, like kitchens and bathrooms, it’s common for water to splash around, so the codes and regulations governing them take that into account.

Laundry room plumbing codes center around the washing machine, just like bathroom codes focus on the toilet, bathtub, shower and sink. In commercial buildings and multifamily dwelling units with a common laundry room, codes may also call for a floor drain.

Plumbing codes aren’t the same everywhere. Some states follow the Universal Plumbing Code (UPC). Others, like California, incorporate the UPC into the state code. Most states follow the International Plumbing Code (IPC). Just to make things interesting, New Jersey conforms to the National Standard Plumbing Code (NSPC).

Because of this variability, when a code question arises, I’ve found the best person to answer it is usually a local plumber.

Laundry Room Plumbing Code: Washing Machine Drain

A washing machine comes with a drain outlet near the bottom where you attach a 1- to 1-1/2-inch flexible hose. The other end of the hose molds into a “J” and fits over the edge of an exposed vertical drain pipe called the standpipe. It must have a minimum diameter to ensure water moves through the drain and doesn’t spill out from the top.

The following standpipe requirements, listed in the California Plumbing Code (CPC), are typical:

• The standpipe diameter is two inches, although some localities allow 1-1/2-inch standpipes. If it connects to a sink drain, the minimum diameter is three inches.
• The standpipe connects to a P-trap. The weir of the trap, which marks the top of the water level inside the inverted “P,” must be from six to 18 inches above the floor.
• The trap is vented by a pipe (minimum 1-1/4-inches in diameter) that rises vertically past the top of the washer before angling to connect to the building’s venting network. In localities that allow air admittance valves (AAVs), you can install one of those instead of a vent pipe. The AAV must remain accessible, which means you can’t bury it behind drywall.
• The standpipe opening is between 18 and 30 inches above the top of the trap. It must rise higher than the flood rim of the washing machine, which is basically the top.

Laundry Room Plumbing Code: Washing Machine Water Supply

Fewer rules govern washing machine water supply lines. Some, like connecting the supply lines to a washer box fastened to the studs, are advisory. That means they make things easier for people using the washing machine, but won’t get you in trouble with a building inspector if you don’t have one.

• Hot and cold supply lines are 1/2-in.-dia. They’re usually copper or PEX, but PVC is also allowable. I prefer PEX because it’s flexible and doesn’t require soldering, something I don’t do well.
• The washer connects to the supply lines via flexible hoses made of braided steel (preferred) or rubber. Flexible hoses usually come with new washing machines. They allow movement of the washer while it’s spinning a heavy load.
• Supply lines stub out behind the washing machine and slightly above it to make them accessible. It’s typical to install the stub outs (or a washer box) 48 inches above the floor.

Laundry Room Plumbing Code: Floor Drain

Plumbing codes generally don’t require a floor drain in the laundry room of a single family residence, but it comes in handy in case of overflows.

If you choose to install one, the drain pipe must have a minimum diameter of two inches. The drain opening, which must have a removable strainer, can’t be under a fixture. The floor needs to slope a minimum of a 1/4-inch per foot toward the drain.

It’s possible to connect the washing machine to the floor drain, but that’s only an option if the drain has a vented trap and empties into the sewer. Draining the washing machine through a floor drain is prohibited if the drain empties into a sump pit.

Other Important Laundry Room Codes

Dryer vent

The International Building Code (IBC), which most states follow some with modifications, sets the rules for dryer venting. They’re intended to prevent lint buildup and possible fires.

• Dryer vents must be four inches in diameter and made of smooth metal. It’s common to use oval or rectangular pipe to fit vents inside 2×4 wall cavities, but some local building codes frown on this, so be sure to check.
• Maximum length is 35 feet with as few sharp bends as possible.
• The vent must extend through the wall and terminate outside the building.
• Flexible plastic dryer vents are prohibited.

Laundry room ventilation

Building codes generally don’t require ventilation in the laundry room. But because of the potential for moisture, mold and wood rot, the Home Ventilation Institute recommends a ducted exhaust fan near the washing machine, especially if there’s no window. It needs to vent outdoors through the roof or a wall, not into the attic or another room in the house.

Electrical requirements

The National Electrical Code (NEC) governs electrical installations, and it’s observed by all states. The NEC requirements specific to laundry rooms include:

• All electrical receptacles must have GFCI protection.
• You need at least one 120-volt, 20-amp receptacle for plugging in the washing machine. It must be connected to the lighting circuit.
• You need a four-prong 240-volt, 30-amp dryer receptacle if you have an electric dryer.

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