Does California Require Dual Plumbing in New Construction?

If you’re planning a new construction project in California—or simply curious about sustainable building practices—you might be wondering: Does California require all new construction to be dual plumbed? With the state’s ongoing drought concerns and aggressive water conservation goals, this question is more relevant than ever. Let’s cut through the confusion and give you the facts you need—clearly, accurately, and with real-world context.

What Is Dual Plumbing?

Dual plumbing refers to a building system that uses two separate piping networks: one for potable (drinkable) water and another for non-potable water, such as graywater (from showers, sinks, and laundry) or reclaimed water (treated wastewater). The goal? To reduce freshwater demand by reusing water for purposes like irrigation, toilet flushing, or cooling systems.

This isn’t just an eco-friendly idea—it’s a practical response to California’s water scarcity challenges. According to the California Department of Water Resources, the state has experienced severe drought conditions for over 8 of the last 15 years, making water efficiency a top priority.

Is Dual Plumbing Mandatory for All New Construction in California?

Short answer: No—not universally.

As of 2025, California does not require dual plumbing in all new residential or commercial construction. However, certain conditions and local jurisdictions may impose such requirements.

Here’s what you need to know:

⚖️ State-Level Requirements

• The California Plumbing Code (CPC), based on the Uniform Plumbing Code (UPC), allows dual plumbing and graywater systems but does not mandate them statewide.
• Title 22 of the California Code of Regulations governs reclaimed water use and sets quality standards—but again, it doesn’t force developers to install dual systems unless a project connects to a municipal reclaimed water supply.

🏙️ Local Ordinances Vary

Some cities and counties go beyond state rules:

• San Francisco: Requires new residential buildings with 3+ units to include plumbing stub-outs for future graywater or reclaimed water connections (SF Health Code Article 19).
• Santa Monica: Offers rebates and fast-track permits for dual plumbing but doesn’t require it—unless part of a larger green building certification (e.g., LEED or CalGreen Tier 2).
• Los Angeles: Under the Green Building Code, certain large developments must include infrastructure for water reuse, though full dual plumbing isn’t always compulsory.

💡 Pro Tip: Always check with your local building department before finalizing plans. Requirements can change rapidly as cities update sustainability goals.

Why Would Builders Choose Dual Plumbing—Even If Not Required?

Even without a mandate, dual plumbing is gaining traction. Here’s why:

According to a 2023 study by the Pacific Institute, buildings with dual plumbing in drought-prone regions reduced potable water demand by up to 40% over five years—proving long-term value.

How Dual Plumbing Works: A Step-by-Step Overview

If you’re considering dual plumbing for a new build, here’s how it’s typically implemented:

1. Design Phase
   • Work with a licensed plumber and civil engineer to map two separate pipe networks.
   • Identify non-potale uses: toilets, irrigation, cooling towers.
   • Ensure compliance with CPC Chapter 17 (graywater) or Chapter 16 (reclaimed water).
2. Rough-In Construction
   • Install purple-colored pipes for reclaimed water (required by code for identification).
   • Include backflow prevention devices and air gaps to prevent cross-contamination.
   • Run dedicated lines from sources (e.g., laundry sinks) to treatment or storage.
3. Treatment (If Needed)
   • Simple graywater (e.g., from laundry) may only need filtration.
   • For toilet flushing, systems often include filtration + disinfection (e.g., UV or chlorine).
4. Inspection & Approval
   • Local health and building departments will inspect for code compliance.
   • Permits vary—some cities require operational permits for ongoing use.

📌 Note: California allows “laundry-to-landscape” systems without a permit for single-family homes (under < 400 gallons/day), but full dual plumbing usually requires approval.

Common Misconceptions About Dual Plumbing in California

Let’s clear up a few myths:

• ❌ Myth: “All new California homes must have dual plumbing since 2023.”
  ✅ Truth: No statewide mandate exists. Only specific cities or project types require it.
• ❌ Myth: “Dual plumbing is too expensive for average builders.”
  ✅ Truth: While upfront costs rise 5–10%, long-term water savings and rebates often offset this within 5–7 years.
• ❌ Myth: “Graywater is unsafe.”
  ✅ Truth: When handled per code (e.g., no kitchen sink water, no storage over 24 hours), graywater poses minimal health risk. The CDC confirms properly managed systems are safe.

For deeper context on water reuse safety, see Wikipedia’s overview on graywater.

Dual Plumbing vs. Traditional Plumbing: Key Differences

FAQ Section

Q1: What exactly is “dual plumbed” in construction terms?
A: It means a building has two separate plumbing systems: one for clean, drinkable water and another for recycled water (like graywater or reclaimed water) used for non-potable purposes.

Q2: Does CalGreen require dual plumbing?
A: Not directly. CalGreen (the California Green Building Standards Code) sets water efficiency targets. Dual plumbing is one way to meet those goals—especially in Tier 2 projects—but it’s not the only option.

Q3: Are there health risks with dual plumbing systems?
A: Only if improperly installed. California code requires color-coded pipes (purple for reclaimed water), backflow preventers, and clear labeling to avoid cross-connection. When installed correctly, risks are negligible.

Q4: Can I install dual plumbing in an existing home?
A: Yes, but it’s costly and disruptive. Retrofitting involves opening walls and floors. That’s why including stub-outs during new construction is highly recommended—even if you don’t activate the system immediately.

Q5: Which California cities require dual plumbing?
A: As of 2025, no city mandates it for all new builds. However, San Francisco, Santa Monica, and parts of Orange County require infrastructure readiness (e.g., pipe stubs) for certain project sizes.

Q6: How much water can I save with dual plumbing?
A: Typical savings range from 30% to 50% of indoor water use. For a 4-person household using 300 gallons/day, that’s 90–150 gallons saved daily—over 54,000 gallons per year.

Conclusion

So, does California require all new construction to be dual plumbed? Not yet—but the trend is moving that way. While there’s no blanket state mandate, forward-thinking builders and municipalities are increasingly adopting dual plumbing to meet sustainability goals, reduce water bills, and prepare for stricter future regulations.

If you’re building new, including dual plumbing infrastructure now could save you money, boost your property’s value, and align with California’s water-resilient future. Even a simple step—like installing pipe stub-outs—positions you ahead of the curve.

Found this helpful? Share it with a builder, architect, or homeowner planning a California project! 🌱💧
Help spread smart water practices—one dual-plumbed home at a time.