Double Your Space: Plumbing a Two Sink Vanity from One

There is nothing quite like the morning rush in a shared bathroom to test the limits of patience and personal space. If you and your partner are constantly elbowing each other out of the way or waiting for the single faucet to free up, you know the struggle all too well. The good news is that upgrading your current setup by plumbing a two sink vanity from a one sink vanity is a highly achievable project that can transform your daily routine. This guide will walk you through the process with clarity and confidence, ensuring you have the dual-sink luxury you deserve without the confusion often associated with complex plumbing tasks.

Is Converting to a Double Vanity Worth the Effort?

Before we dive into the wrenches and pipes, let’s address the elephant in the room: is this renovation actually worth your time and budget? According to recent real estate trends, bathrooms with double vanities often see a higher return on investment (ROI) compared to single-sink setups, particularly in master suites. A study by the National Association of Realtors suggests that bathroom remodels can recoup anywhere from 60% to 70% of their cost upon selling a home, with functional upgrades like additional sinks being a top priority for buyers.

However, it isn’t just about resale value; it is about quality of life. Imagine having your own dedicated mirror, drawer space, and water flow. The psychological benefit of having a defined “his and hers” zone cannot be overstated. While the initial cost involves purchasing a new wider vanity cabinet and countertop, the labor savings of doing the plumbing yourself can significantly offset these expenses.

What Tools and Materials Do You Need Before Starting?

Preparation is the cornerstone of any successful DIY plumbing project. Nothing kills momentum faster than realizing you are missing a critical fitting halfway through draining a pipe. For plumbing a two sink vanity from a one sink vanity, you will need a specific set of tools to ensure clean cuts and leak-free connections.

Essential Tools List:

• Adjustable wrenches (two are recommended for holding nuts steady)
• Pipe cutter or hacksaw (for trimming PVC or PEX pipes)
• Tape measure (precision is key here)
• Level (to ensure your new vanity sits perfectly flat)
• Plumber’s putty or silicone caulk
• Teflon tape (for threading connections)
• Bucket and towels (for inevitable water spills)

Materials Checklist:

• New double-basin vanity cabinet and countertop
• Two sink drains and tailpieces
• Extended P-trap kit (specifically designed for double sinks)
• Supply lines (flexible braided stainless steel is easiest for DIYers)
• Shut-off valves (if your current ones are old or corroded)

It is crucial to measure your existing wall space accurately. Standard single vanities are often 24 to 30 inches wide, whereas double vanities typically start at 48 inches and go up to 72 inches or more. Ensure your bathroom layout can accommodate the extra width without blocking doors or toilets.

How Do You Safely Remove the Old Single Sink Vanity?

Safety first. Before you touch a single bolt, you must shut off the water supply. Locate the shut-off valves under the sink; turn them clockwise until they stop. If these valves are stuck or leaking, you may need to shut off the main water supply to the house. Once the water is off, open the faucet to drain any remaining pressure and water in the lines.

Place your bucket under the P-trap (the U-shaped pipe). Loosen the slip nuts on both ends of the trap using your adjustable wrench. Be prepared for some dirty water to spill out. Once the trap is removed, disconnect the hot and cold supply lines from the faucet.

Next, you will need to detach the vanity from the wall. Most cabinets are screwed into the wall studs at the back. Have a helper support the weight of the cabinet as you remove these screws. If your countertop is glued down with caulk, use a utility knife to slice through the sealant carefully. Lift the old unit away and dispose of it according to your local waste management guidelines. Take this opportunity to inspect the wall for any water damage or mold, which is common behind older vanities.

What Are the Critical Steps for Extending Water Supply Lines?

This is the technical heart of plumbing a two sink vanity from a one sink vanity. Your existing water supply lines are likely centered for one sink, but a double vanity requires water access at two distinct points, usually spaced about 15 to 20 inches apart depending on the sink design.

Step 1: Assess Existing Pipe Access Check where your hot and cold water lines emerge from the wall. If they are flexible copper or PEX lines, you might have enough slack to move them slightly, but rarely enough for a full double setup. You will likely need to install a manifold or extend the lines horizontally.

Step 2: Installing the Extension If you are comfortable with soldering, you can tee off the existing copper lines and run new branches to the left and right. However, for most DIY enthusiasts, using push-to-connect fittings (like SharkBite) or expanding PEX manifolds is safer and requires no open flame.

• Cut the existing supply line carefully.
• Install a T-fitting.
• Run new piping horizontally to the desired location of the second sink.
• Ensure the new drop-down lines are vertical and aligned with the new faucet holes.

Step 3: Pressure Testing Before installing the new vanity, turn the water back on briefly to check for leaks at your new connections. Use a dry paper towel to wipe the joints; even a tiny bead of water indicates a loose fit. Wrap all threaded connections with Teflon tape, winding it clockwise three times for a secure seal.

For a deeper understanding of water distribution systems and pipe materials, you can refer to this comprehensive resource on Plumbing from Wikipedia, which details the history and standards of modern piping.

Step 4: Install New Shut-Off Valves Install individual angle stop valves for both the left and right sinks. This ensures that if one side needs repair in the future, you don’t have to cut water to the entire bathroom. Label them clearly “Left Hot,” “Left Cold,” etc., to avoid confusion later.

How Do You Install the Drainage System for Two Sinks?

Drainage is often more tricky than supply lines because it relies on gravity. When plumbing a two sink vanity from a one sink vanity, you cannot simply connect two traps to one hole; you need a specialized double bowl drain kit.

The Configuration: A standard double sink drain setup uses two P-traps that connect to a central crossover pipe, which then feeds into the main wall drain.

1. Install the Strainers: Apply plumber’s putty around the rim of the drain holes in both sinks. Insert the strainer baskets from the top and tighten the locking nut from underneath. Wipe away excess putty that squeezes out.
2. Attach Tailpieces: Connect the vertical tailpieces to the bottom of each strainer. These should be long enough to reach the level of the P-traps but not so long that they bottom out.
3. Connect the Crossbar: Most double vanity kits come with a horizontal bridge pipe. Connect the outlet of the left P-trap and the right P-trap to this bridge.
4. Final Connection: From the center of the bridge (or from one of the traps, depending on the kit design), run a final tailpiece down to the existing drain pipe in the wall.

Crucial Tip on Slope: Ensure that all horizontal drain pipes have a slight downward slope toward the main exit. Water must flow freely; if a section is level or slopes upward, it will become a breeding ground for clogs and gurgling noises. Use your level to verify a drop of approximately 1/4 inch per foot of pipe.

Tighten all slip nuts by hand first, then give them a quarter-turn with pliers. Over-tightening plastic nuts can crack them, leading to slow leaks inside your cabinet.

Frequently Asked Questions (FAQ)

1. Can I convert a single sink to a double sink without moving the main drain line in the wall?

In most cases, yes. As long as the new double vanity is wide enough to span over the existing central drain, you can use a crossover pipe kit to connect both sinks to that single wall outlet. However, if your new vanity shifts the sinks significantly to the left or right, you may need to extend the drain pipe within the wall, which is a more advanced task.

2. Do I need a permit to replace my vanity and add a second sink?

Regulations vary by location. Generally, replacing fixtures like-for-like doesn’t require a permit, but altering the plumbing layout (adding new supply lines or moving drains) often does. Check with your local building department before starting. Failing to pull a required permit can cause issues when you sell your home.

3. What is the standard distance between the two faucets on a double vanity?

While it depends on the specific vanity model, the standard distance between the centers of the two drains is usually 30 to 36 inches on a 60-inch vanity. Always measure your specific countertop cutouts before buying your plumbing kit to ensure the pipes align correctly.

4. Will adding a second sink reduce water pressure in my shower?

If your home has adequate water pressure and properly sized supply lines (typically ½ inch or larger), adding a second sink should not noticeably affect your shower pressure. However, if you have older galvanized pipes with significant corrosion, the added demand might highlight existing flow restrictions.

5. How do I prevent odors coming from the new double drain setup?

Odors usually indicate a broken water seal in the P-trap. Ensure both P-traps are installed correctly and hold water after every use. Additionally, make sure the venting system in your walls is not blocked. If gurgling occurs, it may indicate a venting issue that requires professional assessment.

6. Is it better to hire a plumber or do this myself?

If you are comfortable using basic tools and following instructions, this is a manageable DIY weekend project that can save you $300–$600 in labor costs. However, if you encounter rot, difficult access, or need to move main supply lines inside the wall, hiring a licensed plumber is the safer and more code-compliant choice.

Conclusion

Transforming your bathroom by plumbing a two sink vanity from a one sink vanity is more than just a cosmetic upgrade; it is an investment in daily harmony and functionality. By following these structured steps—from gathering the right tools and safely removing the old unit to meticulously extending supply lines and configuring the dual drainage system—you can achieve professional results on a DIY budget. Remember, patience and precision are your best friends in plumbing; taking the time to measure twice and test for leaks will save you from headaches down the road.

Now that you have the knowledge to tackle this project, why keep waiting for a crowded morning routine? Grab your toolkit, rally a helper, and start your transformation today. If you found this guide helpful, please share it on your favorite social media platforms to help other homeowners discover the joy of a double-sink sanctuary!