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Single vs. Double Sink Vanity: The 60-Inch Rule, the Second Drain, and the Counter You Give Up
Bathroom Vanities
Single or Double Sink: What the Second Basin Really Costs, and What It Gives Up
Two sinks in the ensuite is on nearly every wish list and off a fair number of them once the plumber has been. Not because it cannot be done, but because a 60 in. double vanity has about as much counter as a 36 in. single, and the second drain is a wall opened up. Here is how to decide with the tape measure instead of the catalogue.
The width rule
48 in.double is possible; nobody is happy
60 in.the standard double; 10 in. counter between
72 in.a double that works like two vanities
30 in.centre-to-centre between sinks, minimum
Two people standing at a counter need about 30 in. each of elbow room, which is why sinks go 30 in. or more apart centre to centre, and why a 48 in. double has the sinks 24 in. apart and two people bumping. At 60 in., the sinks are 30 in. apart and there is about 10 in. of counter between them and 8 in. outside each; the counter is mostly basins. At 72 in., the sinks sit 36 in. apart with real counter between, and it is the first width where a double vanity is better than a single. The NKBA’s bathroom planning guidelines (the sizes and heights page has them) say the same thing in more words.
What it costs
| 36 in. single | 60 in. double | 72 in. double | |
|---|---|---|---|
| Vanity cabinet, mid grade | $900 to $1,600 | $1,600 to $3,000 | $2,000 to $3,800 |
| Quartz top, sinks cut | $700 to $1,100 | $1,200 to $1,900 | $1,400 to $2,200 |
| Sinks and faucets, mid grade | $350 to $600 | $700 to $1,200 | $700 to $1,200 |
| Install, plumbing already there for each sink | $400 to $700 | $600 to $1,000 | $600 to $1,000 |
| Adding a second drain and supplies, wall opened | n/a | $800 to $1,500 | $800 to $1,500 |
| Drywall patch and paint after | n/a | $250 to $500 | $250 to $500 |
| Installed, replacing a single | $2,400 to $4,000 | $5,200 to $9,100 | $5,800 to $10,200 |
Where the plumbing already exists for two sinks (a bathroom that had a double before), take the second-drain and patching lines off and the gap closes to $1,500 to $2,500. Where it does not, the second sink is as much about the wall as the vanity. The vanity calculator has a double option with and without new rough-in; the installation cost page explains the plumbing line.
The second drain, which is the whole plumbing story
Two sinks can share one trap and one drain if they are close enough and the plumber ties them together with a continuous waste under the counter, inside the cabinet, and runs one trap to the existing wall stub-out. The Ontario Building Code allows it for two basins on one trap within set distances, and it saves opening the wall. It is what most 60 in. prefab doubles are built around, and it is the reason a double is sometimes only $600 more to plumb than a single. The alternative, two traps and two wall stub-outs, is cleaner inside the cabinet (more drawer space), is how a plumber will rough in a new bathroom, and in an existing wall is the $800 to $1,500 item. Ask the plumber which one is possible before you buy the vanity, because the vanity’s drawer layout is built around one answer or the other. The plumbing problems page has the rest of what gets found behind the old vanity.
The counter you give up
A 36 in. single with the sink centred has about 10 in. of counter each side, 20 in. total, which is where the toothbrushes, the soap, the glasses and the hair dryer live. A 60 in. double has roughly the same total, split into three small pieces, with the middle one the only useful one. For a couple who get ready at the same time, two basins beats counter. For a couple where one of them leaves at six and the other at eight, or for one person with a lot of things, a 60 in. single with a 48 in. counter beside the basin, and a makeup area at one end, is a better vanity than a double, and it costs less because it is one sink. It is the version designers quietly recommend and homeowners rarely ask for.
When two sinks earn it
- Two adults who use the bathroom at the same time, most days.
- 72 in. or more of wall, or 60 in. and a linen tower or a separate makeup counter elsewhere for the things.
- Existing plumbing for two, or a wall that is open anyway.
- An ensuite in a house that will be sold to a family; buyers count sinks.
- A kids’ bathroom with three or more children and a morning schedule.
When one sink and a long counter is the better bathroom
- 48 to 60 in. of wall. A 60 in. single is a generous vanity; a 60 in. double is two cramped ones.
- The wall is tiled or finished and the second drain would open it.
- One person, or two on different schedules.
- Counter space matters more than simultaneous teeth brushing (which is most households, if they are honest).
- A budget where the extra $2,000 to $4,000 buys a better shower.
Trough sinks and other compromises
A trough sink, one long basin with two faucets, is sold as the answer for a 48 to 54 in. wall. It gives two taps and one drain, which solves the plumbing, and it gives no counter at all, which does not solve the counter. It looks good in a photo and in a hotel. The other compromise is a 60 in. vanity with one offset sink and a long counter, with the rough-in for a second sink stubbed behind the wall for later; the plumber caps it, and the vanity gets changed in ten years without opening the wall. If a double is wanted but the money is not there yet, that is the cheap way to leave the door open.
Questions people ask
What is the minimum width for a double sink vanity?
48 in. is the smallest made and the sinks are too close. 60 in. is the standard. 72 in. is the first width where a double is better than a wide single.
How much does it cost to add a second sink to a bathroom?
If the two basins can share one trap, $600 to $1,000 in extra plumbing. If a second drain and supply pair go into the wall, $800 to $1,500 plus the drywall and paint. Plus the wider vanity, top and second faucet.
Can two sinks share one drain?
Yes, within the distances the plumbing code allows, with a continuous waste under the counter to a single trap. Most 60 in. prefab doubles are designed for it.
Does a double vanity add value?
In an ensuite, buyers expect one in a family house and its absence is noticed. In a hall bathroom, not much. It does not add more than it costs; it removes an objection.
Is a 60 inch single vanity too big?
No. It is the most useful vanity size for one or two people on different schedules: a sink and four feet of counter. It is the one designers pick for themselves.
Measure the wall, then call the plumber
Under 60 in., a single. 60 in. with existing plumbing for two, a double if you both use it at once. 72 in. or more, your call, and the wide single is the sleeper. Price both before deciding.
