Three ways to plumb two sinks
The layout depends on where the wall drain sits and how much room the cabinet gives you.
One wall stub, a tee in the cabinet
The most common setup. Both traps feed a horizontal trap arm that meets a sanitary tee, then a single branch enters the wall at the existing drain.
One stub per sink
Each sink has its own wall drain. This avoids a long shared arm and drains faster, but it means opening the wall to add a stub and a vent connection.
One central stub
A drain centered between the sinks suits a shared tee. It limits the cabinet design to sinks spaced evenly on either side.
Why venting is the part that goes wrong
A drain needs air behind the water. Without a vent, the water leaving one sink can pull the trap seal from the other, which causes gurgling, slow draining and a sewer odor from the dry trap. The vent also lets the line drain without sucking back.
Indiana's plumbing code, 675 IAC 16, sets the rules for trap arm length and vent sizing. A trap arm that runs too far, or too steeply, before reaching a vent will drain badly even when everything is hand tight.
Common problems and what causes them
If a double vanity drains poorly, start with this table.
| Symptom | Likely cause | Fix |
|---|---|---|
| Gurgling when one sink drains | Weak or missing vent | Reroute or add a vent |
| Slow drain in both sinks | Shared arm too flat, or clog | Check slope and clear line |
| Odor from one bowl | Dry or siphoned trap | Run water, check vent |
| Drip under the cabinet | Loose slip nut or washer | Tighten or replace |
| Low flow on one faucet | Kinked or partly closed supply | Check angle stop and line |
What a plumber checks before the install
These checks keep a vanity swap from becoming a wall repair.
- 1
Measure the rough-in
The drain stub height and the distance from the wall, plus the supply stubs for hot and cold, must line up with the new cabinet.
- 2
Check the vent
The vent location and size decide whether a shared drain will work as laid out.
- 3
Trial fit the traps
Traps and arms go in dry first, so the plumber can confirm slope, about a quarter inch per foot, before cementing joints.
- 4
Connect supply lines
Angle stops, braided supply lines and faucets get hand tightened, then snugged with a wrench.
- 5
Fill and test
Both sinks are filled and drained together, so the plumber can watch for gurgling and leaks.
Planning a double vanity and unsure where the drain sits? Call (317) 740-1302 and describe your wall.
☎ Call (317) 740-1302Hard water and permits for an Avon vanity
Citizens Water reports system-wide hardness averaging about 19 grains per gallon, and it varies by treatment plant, so ask Citizens for the figure at your address. Hard water leaves scale in faucet aerators and cartridges, which is a good reason to choose faucets with removable aerators and to keep a small bottle of descaler at hand.
For permit questions on a bathroom remodel, ask the Avon Planning and Building Department, since permit rules vary by job. Indiana licenses plumbing contractors, and you can verify a license at mylicense.in.gov. Local residents with older homes near Avon Avenue may find older supply piping, which a plumber should check at the same time.
Source type: utility water quality report, town building department page and Indiana Professional Licensing AgencySupply lines, shutoffs and WaterSense faucets
Each faucet needs its own pair of angle stops, so you can shut off one sink without losing the other. Faucets with the EPA WaterSense label use less water, which helps when two sinks run at the same time. Replace rubber supply hoses with braided lines when the vanity comes out.
What a homeowner can do and when to call
Swapping a faucet and the visible traps on a vanity where the wall stubs line up is a reasonable DIY job. Take photos first, measure twice, and have the water shut off at the angle stops.
Call a plumber if the drain or vent must move, if you find corroded pipe in the wall, or if two sinks drain slowly after the swap. Our plumbing installation team handles rough-in changes, and our faucet repair team helps with fixtures that leak. The same questions come up for homes in Danville and Brownsburg.
What affects the price of a double vanity install
Get itemized written prices that separate plumbing from cabinetry.
Rough-in changes
Moving a drain or vent means opening the wall, and patching it adds work.
Faucet and fixture type
Widespread faucets and vessel sinks use different parts and labor.
Vanity condition
Old supply lines, shutoffs or traps often get replaced at the same visit.
Access
Tight or finished spaces slow the work.
Homeowners policies typically respond to sudden and accidental damage and typically exclude wear and the failed part itself, so ask your carrier before you rely on coverage.
Call (317) 740-1302 for the real number on your bathroom.
Codes, licensing and 811
Plumbing work in Indiana follows the state plumbing code (675 IAC 16), and the Indiana Plumbing Commission licenses plumbing contractors and journeyman plumbers. You can check any plumber through the license lookup at mylicense.in.gov before work starts, and you should call 811 before any digging.
Codes and standards decide what is allowed on a given job, so ask which ones apply to yours.
Double vanity plumbing questions
Yes, in most homes. The two trap arms meet at a sanitary tee and a single branch enters the wall, as long as slope and venting meet code.
Not always. A shared vent can serve both if the trap arm length stays within the allowed limit. Indiana's plumbing code, 675 IAC 16, sets the rules, so a plumber checks the layout.
Gurgling usually means air cannot get in behind the water, which points to a vent problem or a partial clog. A plumber can test with a camera or a smoke test.
Our line at (317) 740-1302 is answered 24/7, and we offer same-day appointments when available. A vanity install is planned work, but a leak under the sink can be handled outside regular hours.
It can. Citizens reports hard water across its system, so faucets with accessible aerators and cartridges are easier to clean. Ask Citizens for the number at your address.