stesso

Project

This step requires precision. Identify the main vertical drain stack (typically 3" or 4" PVC pipe). At the correct height, use a reciprocating saw to cut out a section of the stack just large enough to fit a new 1-1/2" sanitary tee fitting (using reducer couplings if needed). The tee's sweep must point downwards. Next, assemble the drain arm. Use a PVC cutter or hacksaw to cut sections of 1-1/2" PVC pipe. Deburr the cut ends with a deburring tool or file. Dry-fit all components first. To glue, apply purple PVC primer to the outside of the pipe end and the inside of the fitting socket. While the primer is wet, apply a liberal coat of PVC cement to both surfaces. Firmly push the pipe into the fitting with a quarter-turn twist and hold for 30 seconds to ensure a strong bond. Build the drain arm from the sanitary tee to the vanity location, ensuring a constant downward slope of 1/4 inch per foot. Use a level to check the slope. Terminate the arm with a 90-degree sanitary stub-out elbow that will emerge from the wall. Secure the entire drain arm assembly to the studs using plastic pipe straps and a drill/driver.

You're viewing a step from: How to Rough-In Plumbing for a Bathroom Vanity

Intermediate

30 minutes

2/4 Inventory

This guide provides comprehensive, step-by-step instructions for installing the drain, waste, vent (DWV), and water supply lines within a wall for a new bathroom vanity. It covers planning, accessing the wall cavity, installing PVC drain lines with proper slope, running PEX supply lines, and securing the entire assembly according to standard plumbing practices.

Based on content fromThe Excellent Laborer· 729K subscribers

Frequently Asked Questions

As an "intermediate" project, how challenging is roughing in plumbing for someone with limited prior plumbing experience?

While intermediate, this project requires precision for proper drain slope, watertight PEX connections, and adherence to plumbing codes. Take your time, double-check all measurements and connections, and be prepared to consult diagrams and local regulations. Mistakes in plumbing can be very costly to fix later.

Do I need all the specialized tools listed, like the PEX crimp tool and specific tubing cutters, or are there more budget-friendly alternatives?

Specialized PEX tools are highly recommended for reliable, leak-free connections that meet code. While some PEX systems offer push-to-connect fittings, traditional crimping or expansion tools provide a more robust rough-in. Renting expensive tools like PEX crimpers can be a cost-effective alternative for a one-time project.

Is it always necessary to get a permit and have an inspection for new plumbing rough-in work like this bathroom vanity?

Yes, new plumbing installations almost always require permits and inspections to ensure safety and compliance with local building codes. Failing to obtain permits can lead to costly rework, fines, or issues when selling your home. Always check with your local building department before starting any plumbing work.

What are the most common mistakes DIYers make during a plumbing rough-in, and how can I avoid them, especially regarding leaks?

Common mistakes include improper drain slope leading to clogs, poorly sealed DWV joints, and incorrect PEX connections causing leaks. To avoid these, ensure all PVC joints are dry-fitted and then properly cemented, and that PEX connections are correctly crimped/expanded and burr-free. Always pressure-test the system thoroughly before closing the wall.