What you need before you start

Replacing a Delta bathroom faucet is a job most homeowners can do in an hour or two with basic tools. You will need an adjustable wrench, a Phillips screwdriver, a flathead screwdriver, and a bucket or towel to catch water. Some Delta models also need a hex key (Allen wrench), which often comes in the box. Before you buy a new faucet, measure the distance between the holes on your sink — Delta makes single-hole, center-set (4 inches apart), and widespread (8 inches apart) models, and the wrong size will not fit.

Turn off the water supply under the sink. You will see two shut-off valves, one for hot and one for cold. Turn both clockwise until they stop. Open the faucet to release any remaining pressure in the lines. If you cannot find shut-off valves under your sink, you may need to turn off the main water supply to the house.

Place a bucket or towel under the connections below the sink. Even with the water off, there is usually a small amount of water left in the lines that will spill when you disconnect the supply tubes.

Key Takeaways

  • Turn off both hot and cold water shut-off valves under the sink and open the faucet to release pressure before you disconnect anything.
  • Disconnect the supply tubes from the shut-off valves, then remove the faucet body from above the sink by unbolting the mounting nuts underneath.
  • Clean the sink surface where the old faucet sat, then install the new Delta faucet following the manufacturer's instructions, which vary by model.
  • Reconnect the supply tubes to the new faucet, turn the shut-off valves back on, and check for leaks at every connection before you consider the job done.
  • If you see water dripping from under the sink after you turn the water back on, tighten the connection with your wrench — do not over-tighten, which can crack the fitting.

Removing the old faucet

Disconnect the supply tubes from the shut-off valves by turning the coupling nuts counterclockwise with your adjustable wrench. Hold the valve body steady with one hand so you do not twist the copper line behind it. If the nuts are stuck, spray them with penetrating oil and wait 10 minutes before trying again.

Reach under the sink and locate the mounting nuts that hold the faucet body to the sink. These are usually large nuts on the threaded studs that come down from the faucet. Use your adjustable wrench to turn them counterclockwise. Some Delta models have a center nut; others have two or three nuts depending on the faucet type. Remove all of them. You may need a basin wrench if the space is tight — this tool has a swiveling head that reaches into cramped areas.

Pull the old faucet up and out of the sink from above. The supply tubes will come with it. Set it aside and inspect the sink surface. You will likely see old caulk or mineral deposits where the faucet base sat. Scrape this away with a flathead screwdriver and wipe the area clean with a damp cloth. A clean surface helps the new faucet seal properly and look finished.

Installing the new Delta faucet

Open the box and lay out all the parts. Most Delta faucets come with a rubber gasket or O-ring that goes on the faucet body before it enters the sink. Some models have a metal escutcheon (a decorative ring). Follow the order shown in the instruction sheet — it matters, because putting parts on in the wrong sequence means taking them off again.

Insert the faucet body through the hole or holes in the sink from above. If your sink has three holes and you are installing a single-hole faucet, you will need to cover the unused holes with a deck plate or caps, which Delta usually includes. From underneath, thread the mounting nuts onto the studs and tighten them by hand first, then use your wrench to snug them down. Do not over-tighten — you want the faucet stable, not cracked. A quarter-turn past hand-tight is usually enough.

Attach the supply tubes to the faucet inlets. Most Delta faucets have two inlets marked hot and cold. The hot inlet is usually on the left. Hand-tighten the coupling nuts, then use your wrench to turn them another quarter-turn. Again, snug is better than tight.

Connecting the water supply

Reconnect the supply tubes to the shut-off valves. The tube that came from the hot inlet on the faucet goes to the hot shut-off valve; the cold tube goes to the cold valve. Hand-tighten the coupling nuts first, then use your wrench for a quarter-turn more. If you cross the hot and cold lines, the faucet will work but the handles will be reversed — you can fix this by swapping the tubes.

Turn both shut-off valves counterclockwise to open the water supply. Do this slowly. You may hear air hissing out of the faucet as the lines fill. Let it run for 10 to 15 seconds to push out any air, then turn it off.

Check every connection for drips. Look under the sink at the coupling nuts where the supply tubes meet the shut-off valves and where they meet the faucet. Look at the base of the faucet where it meets the sink. If you see water dripping, tighten that connection a quarter-turn with your wrench and check again. If tightening does not stop the leak, turn the water off, disconnect that fitting, and inspect the rubber washer inside the coupling nut. A worn or missing washer is the most common cause of leaks at these joints.

Testing the handles and spray function

Turn on the hot and cold handles separately to make sure water flows from both. The water may sputter or come out in spurts for the first minute — this is air in the lines and is normal. Let it run until the flow is steady and smooth.

If your new Delta faucet has a pull-down or pull-out spray head, test it by pulling the head toward you or downward (depending on the model) and pressing the trigger. Water should flow from the spray. Release the trigger and push the head back into place. The spray should switch off and water should return to the main spout.

Check the handle operation. Delta faucets use a single lever or dual handles. A single lever should move smoothly from side to side (hot to cold) and up and down (on and off). Dual handles should turn without grinding or catching. If a handle feels stiff, do not force it — you may have installed it incorrectly, and forcing it can damage the cartridge inside.

Sealing the base and finishing

Once you have confirmed there are no leaks and the faucet works, explore a bead of silicone caulk around the base where the faucet meets the sink. Use a caulk gun and a paintable silicone (not acrylic caulk, which cracks). This seals the gap and prevents water from running under the faucet and rotting the cabinet below. Smooth the caulk with a wet finger or a caulk tool, then let it cure for 24 hours before you use the sink heavily.

If your Delta faucet came with an aerator (a small screen that screws onto the spout tip), screw it on by hand. Do not use a wrench — hand-tight is correct. The aerator reduces splashing and saves water.

What to do if something goes wrong

If water leaks from under the sink at a supply tube connection, the coupling nut is loose or the washer is worn. Turn off the water, disconnect the fitting, and look inside the nut. You should see a small rubber washer. If it is missing, cracked, or flattened, replace it with a new one from the hardware store (they cost less than a dollar). If the washer looks fine, reconnect the fitting and tighten it firmly — not with all your strength, but with steady pressure.

If the faucet leaks from the spout when the handles are off, the cartridge inside may not be seated correctly. This is less common with new Delta faucets, but it can happen if the cartridge was installed backward or if debris got into the valve. Turn off the water and remove the handle according to the instruction sheet. The cartridge is the cylindrical part inside. Remove it, rinse it under clean water, and reinstall it, making sure it is fully seated. If the leak continues, the cartridge may be defective and needs to be replaced under warranty.

If you cannot turn off the water at the shut-off valves under the sink because they are stuck or broken, you will need to turn off the main water supply to the house. This is usually a valve near the water meter in the basement or crawl space, or outside near the street. If you cannot find it, call your water company — they can tell you where it is.

Frequently Asked Questions

Do I need to turn off the water to the whole house?

No. The shut-off valves under the sink are there for exactly this reason. Turn both of them off and you can work on the faucet without affecting water anywhere else in the house. If those valves do not work or do not exist, then you will need to shut off the main supply.

Can I reuse the old supply tubes?

You can, but most plumbers recommend replacing them. Supply tubes wear out over time, and if yours are more than 10 years old, the rubber inside may be deteriorating. New braided stainless steel tubes cost $10 to $20 and last much longer. If you do reuse the old tubes, inspect them for cracks or bulges before you reconnect them.

What if my sink has three holes and the new faucet only uses one?

Delta includes a deck plate or hole covers in the box. The deck plate is a flat piece that sits on top of the sink and covers all three holes; the faucet body comes up through the center. Hole covers are small caps that screw into the unused holes. Either way, your sink will look finished and water cannot run into the holes.

How tight should I make the mounting nuts?

Hand-tight plus a quarter-turn with the wrench. The goal is to hold the faucet steady without cracking the sink or the faucet base. If you over-tighten, you risk cracking the porcelain or ceramic. If it is too loose, the faucet will rock and the seal will fail. Start with hand-tight, then use the wrench for just a small turn.

Why is water coming out of both the spout and the spray head at the same time?

The diverter inside the faucet is stuck or installed incorrectly. This is a small valve that directs water either to the spout or to the spray. If it is not working, water goes both ways. Turn off the water and check the instruction sheet to see if the diverter needs to be installed or adjusted. If it is already installed correctly, the diverter may be defective and needs to be replaced under warranty.