Supply Boxes
Plumbing supply boxes are recessed or surface-mounted enclosures that house shut-off valves and, on some models, drain connections for appliances and fixtures. They mount in the wall during rough-in, keep valves reachable after drywall, and let washers, refrigerators, toilets, and sinks connect close to the wall.
Also called a plumbing outlet box, a supply box handles water, drain, or gas connections, not electrical wiring, so it is a different product from an electrical outlet box. The options in this category cover plumbing outlet boxes for appliances in laundry, kitchen, and bathroom installs, plus gas appliance boxes. They include single-valve and dual-valve configurations, copper, PEX, and CPVC inlets, and the trim and replacement parts needed to finish or service each box. Because water supply boxes set the valve location at rough-in, each group below lists the connection type and typical install location.
Product Group Explanation
Supply Box Products
Plumbing supply boxes, also described as plumbing connection boxes, are grouped by the appliance or fixture they serve. Each type below lists its typical connection and install location.
Washing Machine Outlet Boxes
Washing machine outlet boxes house hot and cold shut-off valves and a drain opening for the washer standpipe in one recessed box. Common configurations include 2 in. drain hubs and quarter-turn valves, and some models allow left, right, or center drain positions to suit the framing.
Ice Maker Boxes
Ice maker boxes provide a single cold-water valve for refrigerators with ice makers or water dispensers. Recessing the valve in the wall lets the refrigerator sit closer to the wall without exposed tubing behind it. Boxes are available with copper and PEX inlet connections.
Toilet & Dishwasher Supply Boxes
Toilet and dishwasher supply boxes provide one recessed valve for a single water connection: cold for a toilet, and hot or cold for a dishwasher depending on the appliance. The box conceals the stub-out behind the fixture or inside the sink cabinet and keeps the shut-off accessible.
Lavatory Supply Boxes
Lavatory supply boxes house recessed hot and cold valves for bathroom sinks and vanities. They are used in residential bathrooms and commercial restrooms where supply lines run inside the wall and both shut-offs need to stay reachable below the sink.
Gas Valve Boxes
Gas valve boxes provide a recessed shut-off point behind gas appliances such as ranges, dryers, furnaces, and water heaters. Gas connections fall under fuel-gas code requirements and must be installed and leak tested to local rules.
Supply Box Accessories
Plumbing supply box accessories include faceplates, trim covers, replacement valves, protective debris covers, mounting brackets, and water hammer arrestors for some models. Use them to finish a box after drywall, protect it during construction, or replace a worn valve on boxes built for valve replacement.
How Supply Boxes Work and Where to Use Them
How a Supply Box Works
A supply box mounts to a stud or between studs during rough-in, before drywall. Supply lines connect to the valve inlets, and the valve outlets face the room. After the wall is finished, a faceplate covers the opening and the appliance connects through a supply hose or line. Recessed plumbing supply boxes sit inside the wall cavity, so the appliance can sit closer to the wall.
Residential Applications
Residential plumbing supply boxes are standard in laundry rooms, kitchens, and bathrooms. A washer box behind the machine removes the need for a laundry sink, and an ice maker box keeps the refrigerator line protected.
Commercial and Multifamily Applications
Commercial plumbing supply boxes serve restrooms, multifamily units, and utility spaces where many fixtures repeat one layout. Rated wall assemblies may call for a listed fire-rated box, so confirm the listing against the project specification.
Key Specifications & Planning Steps
Valves and Inlet Connections
Boxes use quarter-turn or multi-turn valves with inlets for copper, PEX, or CPVC. Single-valve boxes serve one water line, and dual-valve boxes handle hot and cold. Some models include integrated water hammer arrestors.
Mounting and Wall Depth
Check stud spacing and cavity depth before ordering. Recessed boxes need room for the box and valves, while surface-mount boxes suit shallow walls and retrofits.
Planning Steps
1. Confirm the appliance, its connections, and the box location.
2. Set the height based on the appliance maker, pedestal use, and local code.
3. Mount and secure the box to the framing.
4. Connect the supply and drain lines, then test for leaks.
5. Finish the wall and install the faceplate.
Choosing the Right Supply Box
Start with the appliance and the connections it needs: hot, cold, drain, or gas. Appliance supply boxes differ mainly in valve count and drain layout, so match the drain hub to the standpipe size and the valve inlets to the supply pipe material. Plastic boxes are lightweight and corrosion resistant, while metal boxes are rigid and suit projects where the specification calls for metal. Confirm wall depth, stud layout, and local code before ordering plumbing supply outlet boxes, and choose models with replaceable valves where future service matters. For the line from the valve to the appliance, see supply lines.
Frequently Asked Questions
Where can I buy plumbing supply boxes for washing machines, ice makers, toilets, and dishwashers in one order?
This category groups plumbing supply boxes for washing machines, ice makers, toilets, dishwashers, lavatories, and gas appliances, along with accessories, so every box for a rough-in can be selected and ordered together.
Where can I buy recessed plumbing supply boxes for washing machines, refrigerators, toilets, and dishwashers?
Recessed versions are listed in the washing machine outlet box, ice maker box, and toilet and dishwasher supply box groups. Recessed plumbing supply boxes mount inside the wall cavity during rough-in.
What is the difference between a plumbing supply box and an electrical outlet box?
A plumbing supply box, also called a plumbing outlet box, houses water, drain, or gas shut-off connections for appliances and fixtures. An electrical outlet box houses wiring and receptacles. They are separate products covered by different codes.
Should I use a recessed or surface-mount plumbing supply box for a remodel?
Use a recessed box when the wall is open and has enough cavity depth for a flush finish. Use a surface-mount box when the wall is shallow or opening it is not practical.
What should I consider when choosing a plastic or metal plumbing supply box?
Consider weight, corrosion resistance, rigidity, the project specification, and installer preference. Plastic boxes are lightweight and corrosion resistant, and metal boxes are rigid. Check the product listing for any rating the wall assembly requires.
How do I choose the right supply box for a washing machine with a 2-inch drain?
Choose a washing machine outlet box with a drain hub that matches the 2 in. standpipe and hot and cold valves that match the supply pipe material. Confirm the drain position (left, right, or center) fits the stud layout.
My refrigerator sticks out too far because of the water line. What type of ice maker box should I use?
Use a recessed ice maker box. It sets the cold-water valve inside the wall, so the line connects without tubing coiled behind the refrigerator and the unit can sit closer to the wall.
How can a washing machine supply box help manage water hammer?
Some washing machine supply boxes include integrated water hammer arrestors that absorb the pressure surge when the washer's valves close quickly. Arrestors are also available as accessories for some models, and local code may require them.
What type of supply box do I need for a gas connection to a dryer or range?
Use a gas valve box, which provides a recessed gas shut-off behind the appliance. Gas connections must meet fuel-gas code requirements and be leak tested after installation.
How can I replace a worn valve or faceplate on a plumbing supply box?
Replacement valves and faceplates are sold as plumbing supply box accessories. On boxes built for valve replacement, the valve swaps out from the front without opening the wall. Shut off the supply before removing the valve.
What kind of supply box goes behind a toilet in a residential or commercial restroom?
A toilet supply box with one recessed cold-water valve. The same box type is used in homes and in restrooms, where commercial plumbing supply boxes keep repeated fixture layouts consistent.
What supply box do I need for a bathroom sink with hot and cold water lines in the wall?
A lavatory supply box. It houses recessed hot and cold valves in one box for sinks and vanities with supply lines inside the wall.
What inlet connection types are available on plumbing supply boxes for copper, PEX, and CPVC?
Water supply boxes are available with copper, PEX, and CPVC inlets. Match the inlet to the supply pipe, and confirm the outlet connection fits the appliance supply line.
What height should a washing machine outlet box be installed at in a laundry room?
There is no single height. It depends on the washer manufacturer's instructions, whether the washer sits on a pedestal, and local plumbing code. Confirm all three before mounting the box.
What accessories do I need to finish or repair a plumbing supply box after installation?
Faceplates or trim covers finish the box after drywall. Protective debris covers guard it during construction, mounting brackets secure it to the framing, and replacement valves handle later repairs. Some models also accept water hammer arrestors.