A deck-mounted faucet connects to your home's water through supply lines that run from the shutoff valves under the sink to the inlets on the faucet. In most US homes the shutoff valve outlet is 3/8 inch compression, while faucet inlets are commonly 1/2 inch threaded (often called IPS) or 3/8 inch compression, so a flexible supply line with the right fitting on each end bridges the two. Wall-mount faucets and shower valves work differently: they connect to pipes inside the wall during rough-in.
The parts in the chain
From the wall to the spout, a typical sink setup includes:
- Supply stub-outs: the hot and cold pipes coming out of the wall or floor, usually 1/2 inch nominal.
- Shutoff valves, often called angle stops, which let you turn off water to that fixture without shutting off the whole house.
- Supply lines: the flexible or rigid tubes connecting each shutoff to the faucet.
- Faucet inlets: threaded shanks or pre-attached lines on the faucet body.
By convention in the US, hot water is on the left and cold on the right when you face the faucet. Keep that orientation when connecting lines so the handles work as expected.
Common sizes and thread types
- 3/8 inch compression: the most common outlet on modern angle stops. A compression nut and ferrule or a gasketed nut seals against the fitting.
- 1/2 inch IPS or NPT: a standard pipe thread size found on many faucet shanks and valves. Supply lines with a 1/2 inch female nut attach to a 1/2 inch male shank.
- 1/2 inch compression: used on some faucets and some older shutoff valves.
Sizes like 3/8 inch and 1/2 inch are nominal names, not the measured outside diameter, which is why matching the fitting type matters more than measuring with a ruler. The product page lists what your faucet uses, and if it is unclear, contact us before buying parts.
Sealing the connection
Compression fittings and gasketed coupling nuts seal mechanically and generally do not need thread tape. Thread sealant tape or pipe dope belongs on tapered pipe threads, such as NPT connections inside a wall. Over-tightening is a common cause of leaks; snug plus a modest turn is usually enough, but follow the manufacturer's instructions.
Choosing supply lines
- Braided stainless steel lines are flexible, widely available and the usual choice for new installs. They come in standard lengths, commonly 12, 16 and 20 inches.
- Rigid copper or chrome-plated risers give a traditional look when visible, as under a pedestal or console sink, but must be cut and bent to fit.
- PEX and other systems may connect differently; your plumber will know what suits your home.
Measure from the shutoff outlet to the faucet inlet and choose a line slightly longer than that distance, allowing a gentle curve without kinks. Replacing old rubber or vinyl lines when you install a new faucet is inexpensive insurance against leaks.
Widespread and bridge faucets
A widespread faucet has three separate pieces on the deck: a spout and two valve handles. Under the counter, each valve connects to the spout through mixing lines, often joined with a tee. Your supply lines then connect to the hot and cold valves. Check that the internal connecting lines are long enough for your hole spacing.
A bridge kitchen faucet has two valve bodies joined above the deck, so it has two supply inlets, one per side. If you add a side sprayer, it typically connects to the faucet's water path through its own hose, so check the faucet and sprayer instructions for how they connect.
Wall-mount faucets and shower valves
Wall-mounted faucets, pot fillers and shower valves connect directly to pipes inside the wall. The plumber sets the valve or rough-in body at the planned height and depth, connects it with threaded, soldered or PEX fittings depending on the system, and pressure tests before the wall is closed. Escutcheons or face plates then cover the openings for a clean finish.
Because these connections are hidden once tile goes up, planning matters. Share the product details with a licensed plumber early and confirm the connection type matches your existing plumbing.
Shop the pieces
- Unlacquered Brass Bridge Kitchen Faucet with Lever Handles: a two-inlet kitchen faucet where checking connection sizes ahead of time keeps the install simple.
- Unlacquered Brass High-Arc Widespread Bathroom Faucet with Lever Handles: a three-piece faucet that shows how valves and spout connect under the deck.
- Unlacquered Brass Wall-Mount Faucet with Lever Handles: for in-wall plumbing planned during a remodel.
- Unlacquered Brass Flat Face Plates: escutcheons that neatly finish wall connections.
See all options in our widespread faucets collection.
Frequently asked questions
Do supply lines come with the faucet?
It varies by product. Check the product page for what is included, or contact us, and buy the right lines before install day.
Should I use thread tape on supply line nuts?
Usually not. Compression and gasketed connections seal without tape. Tape is for tapered pipe threads.
Why is my new connection dripping?
Common causes are a misaligned fitting, a damaged washer, or a nut that is too loose or overtightened. Turn off the water and have it checked.
