Kitchen Plumbing Rough-In
Plumbing rough-in sets up the supply lines and drains for your new kitchen. Whether you're keeping fixtures in place or moving the sink to an island, this work must be done before walls close. Plan carefully—it's expensive to change later.
Quick Summary
Timeline
2-4 days
Typical cost
$2,000-6,000
Moving sink
$500-5,000+
Kitchen Plumbing Connections
A modern kitchen has more water connections than you might think. Plan for everything during rough-in—adding connections later means opening walls.
Essential Connections
- Kitchen sink – Hot/cold supply, drain
- Dishwasher – Hot supply, drain connection
- Garbage disposal – Drain connection
- Gas range/cooktop – Gas supply line
Optional Connections
- Ice maker – Cold water supply to fridge
- Pot filler – Cold supply at range
- Instant hot water – Hot supply at sink
- Water filter – Dedicated filtered tap
Think ahead: Even if you're not installing a pot filler or ice maker now, running the supply lines during rough-in costs very little extra. Adding them later costs much more.
Plumbing Rough-In Process
Plan Fixture Locations
Work with your plumber and cabinet plans to mark exact locations for every water connection. Changes after rough-in are expensive.
Key Dimensions to Provide
- • Sink center location from walls
- • Dishwasher location (usually left of sink)
- • Refrigerator location for ice maker line
- • Range location for gas line
- • Pot filler height (typically 4-6" above cooktop)
Run Supply Lines
Hot and cold water supply lines run from the main lines to each fixture location. Modern installations typically use PEX tubing for flexibility and durability.
PEX Tubing (Recommended)
- • Flexible, easy to route
- • Freeze-resistant
- • No soldering required
- • Less expensive than copper
- • 50+ year lifespan
Copper (Traditional)
- • Long proven track record
- • Recyclable material
- • More expensive
- • Requires soldering
- • Can be affected by acidic water
Important: Install individual shut-off valves at each fixture. This allows repairs without shutting off water to the entire house.
Install Drain Lines
Drain lines are more complex than supply because they rely on gravity. Proper slope and venting are critical for function.
Install Vent Pipes
Every drain needs a vent to work properly. Vents allow air into the drain system, preventing gurgling and slow drains.
Venting Options
- Traditional vent:Pipe runs up through roof. Best option when possible.
- AAV (Air Admittance Valve):One-way valve allows air in. Used when traditional venting isn't practical (common for islands).
- Loop vent:Vent loops up and over, connects to existing vent stack. Sometimes used for islands.
Island sinks: Venting is the tricky part of island sinks. Your plumber may use an AAV or loop vent. Check local code—some areas restrict AAV use.
Run Gas Lines (If Needed)
If you have a gas range or cooktop, a gas supply line runs to the appliance location. This must be done by a licensed plumber.
Safety warning: Never attempt gas work yourself. Gas leaks can cause explosions and carbon monoxide poisoning. Only licensed professionals should work on gas lines.
Gas Line Requirements
- • Proper size pipe for BTU load
- • Accessible shut-off valve near appliance
- • Flexible connector for final connection
- • Pressure test before use
- • Inspection by gas company or inspector
Pass Rough-In Inspection
Before walls close, the plumbing inspector verifies all work meets code. Pressure tests confirm no leaks.
What Inspectors Check
- • Proper pipe sizing
- • Correct drain slope
- • Adequate venting
- • Shut-off valve installation
- • Pressure test (no leaks)
- • Gas line pressure test (if applicable)
Moving the Kitchen Sink
Moving a sink—especially to an island—is one of the most common kitchen remodel requests. The complexity and cost depend on how far it moves.
| Move Type | Cost Range | Complexity |
|---|---|---|
| Minor relocation (2-4 feet) | $500-1,500 | Usually just extending existing lines |
| Same wall, different location | $1,500-3,000 | New drain routing, venting |
| Different wall | $2,000-4,000 | New supply and drain runs |
| To island | $3,000-8,000 | Floor penetration, complex venting |
| Through concrete slab | $5,000-15,000+ | Cutting concrete, structural concerns |
Island sink tip: The drain for an island sink usually runs through the floor. If you have a basement, this is straightforward. On a slab, it requires cutting concrete—a major expense.
Common Plumbing Mistakes
Insufficient drain slope
Drains that are too flat (or have sections that go uphill) cause clogs and slow drainage. Must maintain 1/4" per foot.
Forgetting the ice maker line
Running a water line to the refrigerator location costs almost nothing during rough-in but requires opening walls later.
Inadequate venting
Poor venting causes gurgling drains, slow drainage, and sewer smell. Every drain needs proper venting to function.
Wrong dishwasher drain height
Dishwasher drains need a high loop (or air gap in some codes) to prevent backflow from the sink drain into the dishwasher.
Frequently Asked Questions
How much does it cost to move kitchen plumbing?
Minor relocations cost $500-1,500. Moving to a different wall runs $2,000-4,000. Moving to an island costs $3,000-8,000 due to floor penetration and venting complexity. Slab homes cost significantly more.
What size drain pipe for a kitchen sink?
Kitchen sinks require 1-1/2" or 2" drain pipe. If you have a garbage disposal, 2" is better to prevent clogs. The main drain to the stack should be at least 2".
Do I need a vent for my kitchen sink?
Yes, all drains require venting. Vents allow air in, preventing P-trap siphoning and enabling proper flow. Island sinks often use air admittance valves (AAVs) when traditional venting isn't possible.
Should I add a pot filler during the remodel?
If you want one, now is the time. Running the water line during rough-in costs $300-600 for labor. Retrofitting later means opening walls and costs much more. The fixture itself runs $150-400.
Ready for the Next Step?
With plumbing rough-in complete, it's time for HVAC modifications—ensuring your range hood vents properly and heating and cooling reaches your new kitchen layout.