How do I pick a bathroom sink for a remodel?

The main types differ in how they sit in the countertop, and each one changes the faucet and the cutout.

• Vessel sink. It sits on top of the counter. Kohler's product sheet for a vessel lavatory says the product rests on the countertop, so consider its height when you design the installation, and that the spout must be mounted high enough to clear the 3-1/4 inch rim height and provide a 1 inch air gap per ASME A112.1.2. It also says to choose a faucet that will direct the water stream to the center of the sink.
• Sink built into a vanity top. The faucet mounts through holes in the sink or the top. The IPC says cultured marble vanity tops with an integral lavatory must conform to CSA B45.5/IAPMO Z124.
• Any lavatory. Section 419.1 says lavatories must conform to the listed ASME or CSA product standards, so buy a sink sold as a lavatory.

Kohler's product sheet also says the countertop maker or cutter must use the cutout template provided with the sink or a current one from Kohler, and that the company is not responsible for cutout errors when an incorrect template is used. So decide on the sink before the countertop is cut, and give the fabricator the template.

Match the faucet to the sink's holes and rim. Kohler's lavatory faucet guide says to feed the faucet's supply inlets through the faucet hole of the lavatory and position the faucet, and that if possible you should install the faucet to the lavatory before installing the lavatory. That is easier on a bench or an open cabinet than under a finished counter.

Two checks help:

1. 1Count the holes. The faucet has to match how the sink is drilled. Kohler publishes separate installation guides for single-control and widespread lavatory faucets, which is a hint that the two are not interchangeable.
2. 2Check the spout height. A vessel sink needs a taller spout, per the 3-1/4 inch rim height note above, plus the 1 inch air gap that Kohler cites.

The guide also says to shut off the main water supply, inspect the supply tubing for damage, and replace it as necessary. If the old supply tubes are brittle, a remodel is the time to change them.

The drain is where code sets the numbers. Section 419.3 of the 2024 IPC says lavatories must have a waste outlet not less than 1.25 inches in diameter, and that a strainer, pop-up stopper, crossbar or other device must be provided to restrict the clear opening of the waste outlet. In Chapter 7, Table 709.1 rates a lavatory at 1 drainage fixture unit with a minimum 1.25 inch trap.

Kohler's pop-up drain guide walks through the hardware:

• Vessel sinks need a different gasket. For thin-walled vessel style lavatories, remove the tapered gasket from the drain body and install the thick tapered gasket.
• Seal the flange. Apply plumbers putty or other sealant under the flange, insert the drain body from below, and hand tighten the flange from above.
• Connect the trap. Connect the P-trap to the tailpiece, and check that the plastic washer is inside the flange body or the drain will leak.
• Set the stopper. Adjust it so it lifts about 3/8 inch when opened.
• Test. Check for leaks.

The guide also says that if possible you should install the drain before installing the plumbing fixture.

### What do the trap, overflow and clearances require?

Three more IPC rules matter for placement.

• Overflow. Section 405.8 says that where a fixture has an overflow, the waste must be designed so standing water will not rise in the overflow when the stopper is closed and water will not remain in the overflow when the fixture is empty. Section 405.8.1 says the overflow must discharge into the drainage system on the inlet or fixture side of the trap. Buy the sink and the drain as a matching set for that reason.
• Setting. Section 405.3 says fixtures must be set level and in proper alignment with adjacent walls, and Section 405.6 says the joints where fixtures meet walls or floors must be sealed.
• Clearance. Section 405.3.1 says a lavatory must not be set closer than 15 inches from its center to any side wall, partition, vanity or other obstruction, and there must be at least 21 inches of clearance in front of it to any wall, fixture or door. If the plan puts two sinks in one vanity, the centerlines and the vanity width have to work, so give your designer this number.

Section 405.2 adds that fixtures must be installed so as to allow easy access for cleaning the fixture and the area around it.

That depends on whether the plumbing moves. The City of Phoenix permit exemptions cover clearing stoppages, repairing leaks, and replacing valves or fixtures with compliant new ones, but say a permit is required to relocate any valves, pipes or fixtures. A new sink on the same drain and supply lines is a like-for-like swap. Moving the sink across the room, or adding a second sink, is not. Our page on whether you need a permit to remodel a bathroom in Phoenix explains the test, and what plumbing work needs a permit lists more examples.

If you are considering a faucet that mounts on the wall instead of the counter, our page on installing a wall-mounted bathroom faucet covers the in-wall valve, spout length and permit question.

Work through this checklist with your plumber and your cabinet maker:

1. 1Sink type, and the faucet that goes with it, including the spout height for a vessel sink.
2. 2Number of faucet holes in the sink and the faucet's hole spread.
3. 3Drain and trap: size at least 1.25 inches, with a pop-up or strainer, and the right gasket for a thin-walled vessel.
4. 4Location: 15 inches from the center to the side wall or vanity edge, and 21 inches in front.
5. 5Whether the drain and supply lines stay where they are.
6. 6Who cuts the countertop and with which template.

If you are also planning a kitchen sink, see the difference between an apron and a farmhouse sink, where the weight and the cabinet matter as much as the plumbing. If your current bathroom sink drains slowly, how to fix a slow-draining sink covers the common causes, and what to do about a leak under the sink covers the supply and trap connections that a remodel touches.

HQ Plumbing and Air is licensed and insured, takes emergency calls 24/7, and gives free estimates with an upfront price before work starts. See our plumbing services.