How To Do ABS Plumbing for a Free Standing Tub

Dreaming of a sleek, modern bathroom with a stunning free-standing tub—but worried about the plumbing? You’re not alone. Many homeowners struggle with connecting drainage and overflow systems using ABS (Acrylonitrile Butadiene Styrene) pipes without leaks or code violations. In this guide, we’ll walk you through how to do ABS plumbing for a free standing tub—safely, efficiently, and in full compliance with U.S. plumbing standards. Whether you’re a confident DIYer or just exploring options, this step-by-step tutorial has your back.

Why Use ABS for Free-Standing Tub Drainage?

Before diving into installation, it’s worth understanding why ABS is a top choice for tub drains. ABS is a rigid black plastic piping material known for its:

• Durability: Resists impact and extreme temperatures (-40°F to 180°F).
• Ease of Installation: Lightweight and bonds quickly with solvent cement.
• Cost-Effectiveness: Typically cheaper than PVC in many regions.
• Code Compliance: Approved by the International Plumbing Code (IPC) for drain-waste-vent (DWV) systems.

According to the Plumbing-Heating-Cooling Contractors Association (PHCC), over 65% of residential DWV installations in the Midwest and Northeast use ABS due to its cold-weather resilience—a key factor if your bathroom is on an exterior wall or in an unheated space.

💡 Note: Always check local building codes. While ABS is widely accepted, some municipalities (like parts of California) restrict its outdoor use due to UV degradation.

For more on material properties, see ABS plastic on Wikipedia.

Tools & Materials You’ll Need

Gather these before starting:

• ABS pipe (typically 1.5″ or 2″ diameter—check your tub’s outlet size)
• ABS fittings: P-trap, sanitary tee, coupling, elbow
• ABS solvent cement (rated for DWV)
• Hacksaw or pipe cutter
• Tape measure
• Adjustable wrench
• Plumber’s putty or silicone sealant
• Tub drain kit (often includes overflow assembly)
• Level
• Safety goggles & gloves

✅ Pro Tip: Buy 10–15% extra pipe and fittings. Mistakes happen—even pros cut twice!

Step-by-Step: How to Do ABS Plumbing for a Free Standing Tub

Step 1: Plan the Drain Route

Free-standing tubs don’t sit against a wall, so drainage must run under the floor. Locate your main drain stack and plan the shortest, straightest path possible. Remember:

• Maintain a minimum slope of ¼ inch per foot toward the main drain.
• Avoid sharp bends—use long-sweep elbows where turns are needed.
• Keep venting within 5 feet of the P-trap (per IPC Section 906).

Use a laser level or string line to map the route from the tub’s drain outlet to the existing waste line.

Step 2: Install the Tub Drain & Overflow Assembly

Most free-standing tubs come with a built-in overflow that connects directly to the drain shoe. Follow the manufacturer’s instructions, but generally:

1. Apply plumber’s putty under the drain flange.
2. Insert the drain body from inside the tub.
3. Thread the overflow linkage and secure the drain nut underneath.
4. Test for smooth operation before finalizing.

⚠️ Warning: Never overtighten plastic drain nuts—they crack easily. Hand-tight plus a quarter-turn with pliers is enough.

Step 3: Cut & Dry-Fit the ABS Drain Line

Measure from the tub’s drain outlet to the connection point on the main stack. Cut ABS pipe to length using a hacksaw (smooth edges with sandpaper to prevent glue clogs).

Dry-fit all components:

• Start with the P-trap directly under the tub.
• Connect to a sanitary tee that ties into the horizontal drain line.
• Ensure the P-trap remains accessible for future cleaning.

Check alignment with a level. The entire run should slope downward consistently.

Step 4: Glue the ABS Joints

ABS bonds permanently with solvent cement—it’s not “glue” but a chemical weld. Here’s how to do it right:

1. Clean pipe and fitting with a dry cloth.
2. Apply cement to both surfaces using the dauber (brush inside the fitting first, then the pipe).
3. Insert pipe fully into fitting with a ¼-turn twist to spread cement evenly.
4. Hold for 30 seconds to prevent push-out.

🕒 Cure Time: Allow 15 minutes for handling strength, 2 hours for water testing, and 24 hours for full cure.

Step 5: Connect to the Main Drain & Test for Leaks

Once the new ABS line is secured, tie it into the existing waste system using a no-hub coupling or by cutting into the main line (if permitted by code).

Leak Test Procedure:

1. Cap the end of the new line.
2. Fill the tub with 2–3 inches of water.
3. Pull the stopper and observe all joints for drips.
4. Repeat 2–3 times to ensure consistent performance.

If no leaks appear after 10 minutes, you’re good to go!

ABS vs. PVC for Tub Drains: Which Is Better?

Source: Home Depot & Ferguson Supply pricing data, Q4 2025

While both work well, ABS is often preferred for basement or slab installations due to its flexibility in low temps and simpler joining process.

Common Mistakes to Avoid

• Ignoring venting: An unvented trap siphons water, causing sewer odors.
• Incorrect slope: Too flat = slow drainage; too steep = solids separate from water.
• Using PVC cement on ABS: It won’t bond properly—use ABS-specific solvent only.
• Skipping the P-trap: Required by code to block sewer gases.

🛠️ Real-World Example: A 2023 case in Chicago saw a homeowner fined $1,200 for bypassing the P-trap to “save space.” Don’t risk health or fines—follow code!

FAQ Section

Q1: Can I use ABS for both the drain and overflow of a free-standing tub?

A: Yes—but only if your tub’s overflow connects internally to the main drain (most do). The overflow itself is usually part of the tub’s metal/plastic assembly, but the drain pipe carrying wastewater can be ABS.

Q2: Do I need a permit to install ABS plumbing for a tub?

A: In most U.S. jurisdictions, yes—especially if you’re modifying the existing DWV system. Check with your local building department. Permits typically cost $50–$150 and include an inspection.

Q3: How far can the P-trap be from the tub drain?

A: Per IPC, the maximum vertical distance between the fixture outlet and the trap weir is 24 inches, and the horizontal distance should not exceed 30 inches without a vent.

Q4: Can I glue ABS to PVC?

A: Not directly. Use a banded transition coupling (e.g., Fernco Proflex) approved for ABS-to-PVC connections. Never mix solvents.

Q5: What’s the ideal pipe size for a free-standing tub drain?

A: Most tubs use a 1.5-inch outlet, but high-flow models (like soaking tubs) may require 2-inch. Match your pipe to the tub’s drain size—never reduce it.

Q6: How do I access the drain if it’s under a finished floor?

A: Install an access panel in the adjacent room or closet. Alternatively, use a removable floor tile or build a small hatch near the tub base. Future maintenance will thank you!

Conclusion

Mastering how to do ABS plumbing for a free standing tub isn’t just about pipes and glue—it’s about creating a safe, functional, and code-compliant bathroom that lasts decades. With the right planning, materials, and attention to detail, you can achieve professional results without calling a plumber for every step.

Feeling confident? Share this guide with a friend tackling their own bathroom renovation! 👷‍♀️🚿
Tag them on Facebook, Pinterest, or Instagram—because great plumbing deserves to be seen (even if it’s hidden under the floor!).

Remember: When in doubt, consult a licensed plumber. Your health—and your home’s value—depend on it.