Lavatories: Wall-Hung, Vanity, and Vessel Types

Lavatories: Wall-Hung, Vanity, and Vessel Types

A lavatory is any plumbing fixture designed for handwashing. The three types you will encounter most in residential and light commercial work are the drop-in (vanity), wall-hung, and vessel lavatory. Each type shares the same basic drain and supply connections, but differs in how it is supported and how it seals to the surrounding surface.

Types of Lavatories

Drop-in (self-rimming) lavatory: The basin drops into a hole cut in a vanity top. The rim rests on the countertop surface and is sealed with plumber's putty or silicone caulk, depending on the countertop material. Silicone is preferred on stone and solid-surface tops because putty can stain them. Drop-in lavatories are popular in residential bathrooms because they are straightforward to install and easy to replace.

Wall-hung lavatory: This fixture mounts on a carrier or hanger bracket that is fastened directly to wall framing or a steel carrier frame built into the wall. The fixture bears its full load — including the weight of a person leaning on it — through that bracket. Proper blocking or carrier installation during rough-in is essential; a poorly supported wall-hung lavatory is a falling hazard. Wall-hung fixtures are common in commercial restrooms and ADA-accessible installations because the open space beneath them allows wheelchair approach.

Vessel lavatory: The basin sits on top of the counter rather than dropping into it. The drain opening in the counter must align with the vessel drain fitting. Because the basin rim is elevated, the faucet must be tall enough to clear it. Vessel lavatories are a design choice seen in higher-end residential work.

This lab focuses on the drop-in and wall-hung types.

The Pop-Up Drain Assembly

Most lavatories use a pop-up drain rather than a simple strainer. The assembly consists of:

• Drain body (tailpiece extension): Threads into or seats in the drain hole of the lavatory.
• Pop-up stopper: Sits in the drain opening; a slot or hole on its side engages the pivot rod.
• Pivot rod: Passes through the drain body horizontally; its ball seats in a socket on the drain body and its tip fits into the stopper slot.
• Clevis strap: A slotted metal strip connected to the pivot rod at the bottom and to the lift rod at the top.
• Lift rod: The knob that passes through the faucet body. Pushing it down raises the stopper; pulling it up lowers the stopper.

Adjustment is made by moving the pivot rod to a different hole in the clevis strap (changes the range of stopper travel) and by loosening the clevis screw to slide the strap up or down relative to the lift rod (changes the resting position). Always test by filling the basin partway and confirming the stopper holds water before completing the installation.

The P-Trap and Drain Connection

Every lavatory requires a trap to prevent sewer gas from entering the building. For lavatories, a 1-1/4 in. P-trap is standard (some jurisdictions accept 1-1/2 in.; verify local code). The trap has two functional requirements:

1. Trap seal: Water must remain in the curved section — typically a minimum depth of 2 inches — to block gas. After installation, fill the basin and let it drain; water retained in the trap confirms the seal.

2. Trap arm slope: The horizontal arm running from the trap outlet to the drain stub-out must slope downward toward the drain. A slight downward pitch — commonly stated as 1/4 inch per foot — prevents standing water in the arm while keeping enough slope to self-clean. A trap arm that runs uphill can lose its seal; one that drops too steeply can siphon the trap dry.

Connect the trap with slip-joint nuts and washers. Hand-tighten, then snug with pliers — do not over-torque plastic fittings.

Angle Stops and Supply Risers

Angle stops (also called angle supply valves) are the shutoff valves installed at the wall or floor stub-outs beneath the lavatory. The inlet typically connects to a 1/2 in. IPS or compression fitting on the supply stub-out; the outlet accepts the supply riser. Hot supply is connected to the left angle stop and cold to the right when facing the fixture — this is standard trade practice and aligns with faucet port orientation. Always verify that both angle stops close fully before starting work, and open them slowly when testing to avoid water hammer.

Supply risers run from the angle stop outlet to the faucet inlet shanks beneath the lavatory. Braided stainless-steel flexible risers are common in finish work. Use a basin wrench to reach and tighten the mounting nut and supply connections in the confined space behind the drain.

Wall-Hung Lavatory Installation

Before the wall is closed during rough-in, the carrier bracket or steel carrier frame must be set at the correct mounting height. For a standard installation, the rim of the lavatory is typically set at a height suited to the user; ADA guidelines specify a maximum rim height for accessible fixtures — consult the applicable standard for the project. Secure the carrier to solid framing or blocking. When hanging the lavatory, confirm it is level both front-to-back and side-to-side before making any connections.

Safety

• Wear safety glasses and nitrile gloves throughout the lab. Plumber's putty and pipe-joint compounds can irritate skin; gloves protect against sharp edges on fixture hardware.
• Before connecting supplies, confirm angle stops are closed and the water source is isolated.
• When handling a wall-hung lavatory, use a partner — these fixtures are heavy and awkward; a dropped fixture can cause serious foot injury.
• Inspect all plastic trap and riser fittings for cracks before assembly. A cracked fitting will fail under water pressure.
• Clean up spilled water immediately to prevent slip hazards.

Pass Criteria

Your lab is complete when: all supply and drain joints are dry after a full fill-and-drain test; the pop-up stopper opens and closes through its full range; a visible trap seal is present; and the trap arm slopes toward the drain. All four criteria must be met.