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Should a double sink have two traps?

Author

David Ramirez

Updated on March 12, 2026

Should a double sink have two traps?

Speaking from personal experience, only use one trap in a dual sink bathroom. With two traps, you can get air pockets blocking one or the other's drain. Normally, these double tees are used for adjoining bathrooms, so you can have a sink on each side of the wall, and share the same stack.

In respect to this, does a double sink need 2 traps?

A double bathroom sink installation rarely requires more than one P-trap. The usual practice is to connect the two sinks to a tee and then feed the tee into a single P-trap, which then connects to the drain.

Secondly, can you connect two sinks to one drain? In most cases, you can easily adapt the supply and drain pipes to accommodate two sinks, using tee fittings, special valves, extension pipes and hoses. You may have to vent each sink separately, though, depending on your local plumbing codes.

Regarding this, is it OK to have 2 P traps?

2 Answers. Yes, in most every home, multiple P traps eventually go into a single drain. What you can't have is one P trap in line with another (creating an air locked section), but two P traps that connect to a Y and enter the wall should be perfectly fine.

How far apart should double sinks be?

36 inches

How much does it cost to add a second sink?

This second scenario is what we'll describe in this project. According to ImproveNet, this bathroom improvement cost roughly $400, on average.

Does AP Trap have to be directly under the drain?

The "P" trap SHOULD be directly under the drain, but no more than a few inches off center of it, if conditions require it.

What is considered an S trap?

A common plumbing defect found in many older houses is an “S” trap. An “S” trap is named so because it looks like an “S” on its side – it basically consists of a normal trap, and then another trap installed right up against it in an upside-down fashion, as shown below. When water sits in the trap, sewer gases stay out.

Are P traps required?

Plumbing codes require a P-trap be installed anywhere there is an open drain line that expels wastewater into a drain waste-vent system. The P-trap traps solids that can clog the drain or sewer line. The P-trap stops sewer gases from backing into your home through the drain line.

What's the difference between an S trap and P trap?

The "trap" is the bend in the pipe where the waste goes out of the toilet. An S-trap exits at the bottom of the toilet, and is designed to outlet directly through the floor, where a P-trap exits at the back of the toilet and is designed to outlet through a wall.

How do you drain a double kitchen sink?

Run horizontal pipes from both drains and connect them to each other with a double 90-degree drain tee if the drain is located mid-way between the sinks. Fit a short length of pipe into the bottom of the double tee and connect the P-trap to that pipe. Extend the horizontal outlet arm of the trap to the wall drain.

Why is an S trap illegal?

The purpose of a trap is to prevent sewer gases, and possibly vermin, from coming in to the home. Back to “S” traps – The reason “S” traps aren't allowed is because they have the potential to suck, or 'siphon', water out of the trap as the water flows down the drain.

Can you add a second sink?

Creating a double-sink vanity top generally involves one of two scenarios: Either you are installing an all-new countertop, probably one that already has two basin cutouts; or you are installing a second sink alongside the first sink by cutting an opening in the countertop and adding the water supply and drain lines to

Can AP Trap be too deep?

When the trap is too deep, liquid may flow through it too fast, which can lead to siphoning of the trap seal and sludge buildup. If installing a sink with a deeper bowl results in a trap seal deeper than 4 inches, you'll have to open up the wall and relocate the trap arm connection at the drain (see photo, above).

How far down does a shower drain go?

about 3/4 to 1 inch

What is AP Trap?

A P trap is a plumbing device which prevents odorous gas in plumbing drains and sewers from rising up through a toilet, sink or floor drain into a home or business. A P trap is a U-shaped section of pipe that holds water as shown in the diagram below.

How long is ap trap arm?

Maximum Distance
However, the Universal Plumbing Code stipulates that the total developed length of all tailpieces, arms and fittings connecting the drain to the p-trap must be 24 inches or less.

Can you add a second sink in bathroom?

There are certainly much more complicated plumbing improvements that DIYers perform, but adding a second vanity sink does require some broad plumbing skills and experience. A diverse range of plumbing skills is required since you will be connecting both water supply and drain pipes.

Can two drains share a vent?

It's common to use a 1 1/2-inch vent for a 2-inch drain because that ensures that the drain will get enough air. It can then run horizontally to tie into another vent, as long as it maintains a 1/4-inch-per-foot slope toward the drain.

Can you put a vessel sink over an existing sink?

Technically you can put a vessel sink on any cabinet. The issues involved though include the height of the cabinet, whether it has an existing countertop or not, and your current plumbing.

How many sinks can you have on two drains?

710.1 Maximum Fixture Unit Load
DIAMETER OF PIPE (inches)MAXIMUM NUMBER OF DRAINAGE FIXTURE UNITS (dfu)
Total for horizontal branchTotal for stack of three branch Intervals or less
11/234
2610
21/21220

Does a double sink add value?

If you install two sinks and two mirrors (or one large mirror), you will each have your own space to perform your morning and evening rituals. Because so many couples prefer to each have their own sinks, an upgrade like this can be a big selling point and can add value to your home, if you do the job right.

How long should a double sink vanity be?

Know that most single sink designs are 36 to 48 inches wide. Double sink vanities, on the other hand, usually measure 60 to 72 inches. There are some 60 to 72 inch vanities that also come in a single sink version.

How small can a double sink vanity be?

For baseline, minimum access, locate the centerline of a lav at least 15 inches from a side wall and space double lavs a minimum of 30 inches from center to center. For more comfortable use, allow at least 3 feet of wall space per user and 42 inches for a single vanity width.

Does a double vanity add value?

Because so many couples prefer to each have their own sinks, an upgrade like this can be a big selling point and can add value to your home, if you do the job right. Measure out the space you have available for vanities in your bathroom. It's much more expensive to plumb two sinks than it is to plumb a single one.

How wide should a double sink vanity be?

Know that most single sink designs are 36 to 48 inches wide. Double sink vanities, on the other hand, usually measure 60 to 72 inches. There are some 60 to 72 inch vanities that also come in a single sink version. The determining factor should be how you plan on using the space.

How much space do you need between toilet and sink?

A toilet requires a minimum 30 inches of space to sit in by itself: 15 inches from the center line out to each side. Sinks require a minimum of 20 inches of space to sit in, if they are the only sink in the room. Showers require a minimum of 30 inches of space into which a 30 inch diameter circle could be drawn.

How much space should be between sink and wall?

Place the bathroom sinks 20 inches from the back wall, recommended. The bare minimum is 15 inches. This is measured from the sink's center line to the wall.

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Should a double sink have two traps?