Run Rough Plumbing Lines
Install water supply and drain lines for basement bathrooms, wet bars, and laundry areas. Proper planning ensures code compliance and leak-free operation.
Why Proper Plumbing Installation Matters
Plumbing rough-in is the most complex and critical mechanical system in your basement. Mistakes cause devastating water damage, sewer gas infiltration, and costly repairs. Unlike electrical work, plumbing errors often don't appear until water is running - after walls are closed. Proper drain slopes prevent clogs. Correct venting prevents siphoning and sewer gas entry. Well-supported pipes don't leak or vibrate. This isn't work to rush or guess at - follow codes precisely or hire professionals. The cost of proper rough plumbing is nothing compared to tearing out finished walls to fix leaks or adding venting that was missed.
Tools & Materials Needed
Tools
Materials
Step-by-Step Guide
Plan Drain and Vent System
Design your drainage system following plumbing codes:
Key Planning Points:
- •Slope: Minimum 1/4" per foot for all drain lines
- •Pipe Sizing: 3" for toilets, 2" for showers, 1.5" for sinks
- •Venting: Every fixture needs venting to prevent siphoning
- •Cleanouts: Required every 100' and at direction changes
- •P-traps: Every drain fixture must have a trap
Consider Hiring: Drain/vent layout is complex with strict code requirements. Many homeowners hire a plumber just for design consultation ($200-400) then do installation themselves.
Install Sewage Ejector Pump (If Needed)
Most basement bathrooms require a pump to lift waste to main sewer line:
- Dig pit for sewage basin (typically 18-24" diameter x 24-30" deep)
- Set basin in pit on gravel base, ensure it's level
- Break through concrete floor if necessary for inlet and outlet pipes
- Install pump in basin according to manufacturer instructions
- Run discharge pipe from pump to connection point on main drain
- Install check valve on discharge line to prevent backflow
- Wire pump to dedicated GFCI-protected circuit with float switch
- Install air-tight cover with vent connection
Important: Sewage pump installation often requires breaking concrete, extensive excavation, and precise electrical work. This is typically a job for professionals unless you have plumbing experience.
Run Drain Lines
Install PVC or ABS drain pipes from fixtures to main drain or sewage pump:
- •Start from main connection point and work toward fixtures
- •Cut pipes square using PVC saw or miter saw
- •Deburr all cuts and dry-fit entire system first
- •Use level to verify 1/4" per foot slope throughout
- •Apply primer then cement to all joints, twist 1/4 turn
- •Support pipes every 4 feet with proper hangers
- •Install cleanout fittings at required locations
Install Vent Pipes
Every drain needs proper venting to work correctly:
Vents must be 6" above flood rim of highest fixture. If running through roof, extend 12" minimum above roof surface and install proper flashing and vent cap.
Test Drain System
Test for leaks before covering pipes with insulation or drywall:
Water Test:
- Cap all drain openings with test caps
- Fill system with water from highest point
- Let stand for 15-30 minutes
- Inspect all joints for leaks
- Mark and repair any leaks, retest
Air Test (Required by Some Codes):
- Cap all openings including vents
- Pressurize system to 5 PSI with air compressor
- System must hold pressure for 15 minutes minimum
- Any pressure drop indicates leak
Run Water Supply Lines
Install hot and cold water lines using PEX or copper:
- •Use 3/4" for main runs, 1/2" for individual fixtures
- •Install shut-off valves at main connection points
- •Run separate hot and cold lines to each fixture
- •Secure PEX every 32" with plastic hangers (allows expansion)
- •Keep supply lines 6" away from drain/vent pipes
- •Stub out at fixture rough-in heights per code
- •Pressure test at 80 PSI for 2 hours, inspect for leaks
Pro Tip: Use a PEX manifold system for easier installation and better control. Each fixture gets dedicated hot and cold lines from a central manifold with individual shut-offs.
Pro Tips
- ✓Take photos of all plumbing before covering - invaluable for future repairs or additions
- ✓Color code PEX lines - red for hot, blue for cold makes identification easy forever
- ✓Install a floor drain near the sewage pump in case of pump failure or overflow
- ✓Add extra cleanouts beyond minimum - makes future drain cleaning much easier
- ✓Seriously consider hiring a plumber for drain/vent work - this is where most DIY mistakes happen
Frequently Asked Questions
Do I need a sewage ejector pump for a basement bathroom?▼
If your basement bathroom drains are below the main sewer line or septic tank level, you need a sewage ejector pump (also called sewage pump or grinder pump). The pump collects waste in a basin and pumps it up to the main drain line. Most basement bathrooms require this because they're below grade. Only if your home is on a hill with the basement at a level above the sewer connection can you drain by gravity.
What slope do basement drain pipes need?▼
Drain pipes must slope at minimum 1/4 inch per foot (2% grade) for pipes 3 inches and larger, and 1/4 inch per foot minimum for smaller pipes. The standard is 1/4 inch per foot for most residential drains. Too little slope causes slow drainage and clogs. Too much slope (over 1/2 inch per foot) can cause problems with solid waste separation. Use a level to verify slope throughout the run.
Should I use PEX or copper for basement water lines?▼
PEX is generally better for basement applications. It's more affordable ($0.50-1.50/ft vs $2-4/ft for copper), easier to install with fewer fittings, resistant to freezing and bursting, and flexible for easier routing. Copper is more durable long-term and better if exposed aesthetically, but PEX is the standard for modern residential rough plumbing. Both are code-approved - choose based on budget and preference.
Can I do my own basement plumbing or do I need a plumber?▼
This depends on local codes and your skill level. Many areas allow homeowner plumbing with permits and inspections. However, plumbing requires understanding drain slopes, venting requirements, pipe sizing, and proper connections. Mistakes cause leaks, sewer gas entry, and code violations. Most homeowners should hire a licensed plumber for drain/vent work and sewage pump installation, then possibly do their own water supply lines. Always get required permits and inspections regardless of who does the work.