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Replacing a kitchen faucet involves two supply connections and a mounting nut. That is the whole of it. What makes the job a struggle is that all three are reached by lying on your back inside a cabinet, and the old nuts have had twenty years to seize. Plan for that, and it goes smoothly.
Before you buy
Count the holes in the sink or the countertop. A faucet with a single post covers one hole; a deck plate covers up to three. A separate sprayer or a soap dispenser uses a hole of its own. Buy a faucet that suits the holes you have, or one that comes with a deck plate to cover the extras.
Check the supply lines. Many new faucets come with their own flexible lines; if not, buy two braided stainless faucet supply lines in the right length, with the fitting that matches your shut-off valves, usually 3/8 inch compression.
Tools
- A basin wrench, the long-handled tool that reaches the nuts behind the sink. It costs little and turns this job from an ordeal into a chore.
- Adjustable wrench and pliers
- A flashlight or a headlamp, a bucket, towels
- Penetrating oil for stuck nuts
Removing the old faucet
- Close both shut-off valves under the sink, and open the faucet to check the water has stopped. If a valve will not close, or drips when you turn it, stop: that is the point where the job becomes a plumber's.
- Put the bucket under the connections. Unscrew the supply lines from the valves, then from the faucet.
- If there is a sprayer, disconnect its hose and the weight.
- Find the mounting nuts up behind the sink, holding the faucet down. Spray them with penetrating oil, wait, and undo them with the basin wrench. Plastic nuts may turn by hand.
- Lift the old faucet out from above. Scrape off the old putty or gasket and clean the surface.
Fitting the new one
- Feed the new faucet's lines and post down through the hole, with its gasket or deck plate in place. Some makers ask for a bead of plumber's putty under the plate; follow the instructions.
- From below, slide on the washer and mounting nut and tighten. Have someone hold the faucet straight from above, or check it between turns.
- Connect the supply lines to the faucet, then to the valves. Hand tight plus a quarter turn. The rubber washer or the compression fitting makes the seal, not force.
- For a pull-down sprayer, connect the hose and clip on the weight as instructed.
- Remove the aerator from the spout, open the valves slowly, and run both hot and cold for a minute to flush out debris. Refit the aerator.
- Check every connection with a dry paper towel, then again an hour later.
Common snags
- The old nuts will not move. More penetrating oil, more time, and the basin wrench. A nut splitter or a reciprocating saw is the last resort, cutting the old faucet away from below.
- The supply lines are too short or the wrong fitting. Measure before you buy, and take a photo of the valve outlet to the store.
- A drip at a compression fitting. A further quarter turn. If it continues, undo it, check the ferrule is seated, and redo.
- Low flow from the new faucet. Debris in the aerator or the cartridge from the flush. Clean the aerator.
When to call a plumber
- Shut-off valves that will not close or that leak
- Corroded pipes under the sink
- A faucet you cannot remove without damaging the sink
- If you would rather spend the afternoon differently: a plumber does this in about an hour
Find a licensed plumber near your town.