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Lavatory drain rough-in — Planning and Layout

Intermediate

Part of project

How to Rough-In Plumbing for a Bathroom Vanity · Step 1 of 8

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Install the bath lavatory drain in the center of the vanity. The center of the drain should be approximately 18 inches above the finished floor. Use an inch and a half sanitary tee in the vertical position. The water lines should be roughed in approximately 21 inches above the finished floor and spaced about 8 inches apart.

Goal: Install lavatory drain

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FAQs

How difficult is it to rough-in plumbing for a vanity, and how long should I expect it to take?

This project is rated "intermediate" because it requires precise measurements, proper pipe joining techniques, and an understanding of plumbing codes. For a DIYer with some experience, expect 8-16 hours of work, depending on existing wall access and any unforeseen issues. Costs can range from $150-$300 for materials, assuming you already own basic tools.

What are the most crucial safety precautions I should take when roughing-in plumbing?

Always shut off the main water supply before cutting into existing lines to prevent flooding. Wear appropriate personal protective equipment (PPE) like safety glasses, gloves, and hearing protection, especially when using power tools like drills and hole saws. Be mindful of electrical wires inside walls when drilling or cutting.

The guide mentions PEX for supply lines; can I use copper or CPVC instead, and what are the pros of PEX?

While copper and CPVC are alternatives, PEX is often preferred for DIY projects due to its flexibility, ease of installation (fewer fittings, no soldering), and resistance to freezing. However, PEX requires specific crimp or expansion tools. If you're comfortable with soldering, copper is a durable choice, and CPVC offers a rigid, solvent-weld option.

What are the most common mistakes DIYers make when roughing-in a vanity's drain and supply lines?

A common mistake is incorrect drain slope, leading to clogs – ensure a 1/4 inch per foot slope for DWV lines. Another error is misplacing supply stub-outs, making fixture installation difficult; always double-check vanity and sink specifications. Also, failing to properly prime and cement PVC joints can cause leaks.

Lavatory drain rough-in — How to Rough-In Plumbing for a Bathroom Vanity (Step 1, Video 2) | Stesso