How To Plumb A 3-Compartment Restaurant Sink (Step-by-Step Guide for Code Compliance)

Why Getting Your 3-Compartment Sink Plumbed Right Matters More Than You Think

If you run a restaurant, bar, or food truck, you know how critical a clean, compliant sink is—not just for hygiene, but for keeping your business open. A poorly plumbed 3-compartment sink doesn’t just look messy; it can trigger a health department violation, shut you down for days, or even cost you your license.

That’s why how to plumb a 3-compartment restaurant sink isn’t just a DIY project—it’s a legal and safety imperative. In fact, 68% of health code violations in U.S. food establishments stem from improper sink setup, according to the CDC’s Foodborne Outbreak Surveillance System.

Don’t panic. You don’t need to be a plumber to get this right. This guide walks you through every step—clearly, safely, and in full compliance with FDA Food Code and local plumbing regulations.

What Are the 3 Compartments For? (And Why Plumbing Matters)

Before you touch a pipe, understand the purpose of each compartment:

Source: FDA Food Code 2022, Section 3-501.11

If your plumbing doesn’t deliver the right water temperature, flow rate, or drainage to each compartment, you’re not just cutting corners—you’re risking foodborne illness.

“A sink that doesn’t meet temperature or flow standards is essentially useless,” says Dr. Linda Harris, food safety expert at UC Davis. “Sanitation isn’t about scrubbing harder—it’s about engineering the right environment.”

Step 1: Check Local Plumbing Codes Before You Start

Every state and county has its own plumbing code, often based on the International Plumbing Code (IPC) or Uniform Plumbing Code (UPC). But here’s the catch: health departments enforce sanitation rules, while plumbing inspectors enforce pipe specs.

👉 Action Step:
Call your local health department or building authority. Ask:

• What’s the minimum drain size required?
• Is an air gap mandatory for the third compartment?
• Do I need a grease trap?

Pro Tip: Most jurisdictions require a minimum 2-inch drain pipe for 3-compartment sinks. Some mandate a 3-inch drain if it’s in a high-volume kitchen.

💡 Did You Know? The CDC reports that 1 in 6 Americans get sick from contaminated food each year—many linked to improper sanitation equipment. Your sink is your first line of defense.

Step 2: Gather the Right Tools & Materials

You don’t need a professional toolkit—but you do need the right parts:

Avoid cheap plastic parts. They crack, harbor bacteria, and violate NSF/ANSI 2.

Step 3: Install the Sink & Connect the Drain System (Step-by-Step)

Step 3.1: Position the Sink

• Place the sink near your prep area, but away from raw meat stations to avoid cross-contamination.
• Leave at least 18” clearance on all sides for cleaning and access.

Step 3.2: Connect the Wash Compartment (Compartment 1)

• Run a hot water line from your water heater to this compartment.
• Set temperature to 110°F–120°F (use a thermometer). Too hot? You’ll scald hands. Too cold? Detergent won’t work.
• Install a single-handle mixing valve for easy temp control.

Step 3.3: Connect the Rinse Compartment (Compartment 2)

• Use clean, cold or lukewarm water (no detergent).
• This line should come from the same cold water supply as your faucet—no mixing valve needed.
• Ensure the water flows freely—no pressure drop.

Step 3.4: Connect the Sanitize Compartment (Compartment 3)

You have two options:

⚠️ Critical Rule: If you use chemical sanitizer (like chlorine or quaternary ammonium), you MUST install an air gap. This prevents dirty drain water from siphoning back into your sanitizing water—a major FDA violation.

How to install an air gap:

1. Mount the air gap fitting above the sink rim (minimum 1” above highest water level).
2. Connect the drain line from the sink to the air gap inlet.
3. Run a second line from the air gap outlet to the drain pipe.
   (See diagram on Wikipedia: Air Gap (plumbing) ) — this is a federally mandated safety feature.)

Step 3.5: Drain System Setup

• All three compartments must drain into a single 2” or 3” P-trap.
• The trap must be installed within 3 feet of the sink.
• Slope the drain line 1/4 inch per foot toward the main sewer line.
• Install a grease interceptor if your sink will handle greasy dishwater (required in most commercial kitchens).

✅ Pro Tip: Test your drain with 2 gallons of water. If it takes longer than 15 seconds to drain, your slope is too shallow. Fix it now—before inspection.

Step 4: Test for Compliance Before Opening

Before you serve your first meal, do this checklist:

📌 Real Case: A taco truck in Austin failed inspection because their sanitize compartment was plumbed directly into the drain—no air gap. They were shut down for 11 days. Cost: $18,000 in lost revenue. All because they skipped step 3.4.

Common Mistakes (And How to Avoid Them)

FAQ: Your Top 6 Questions About 3-Compartment Sink Plumbing

Q1: Can I use a regular kitchen sink instead of a 3-compartment sink?

No. FDA Food Code §3-501.11 requires a dedicated 3-compartment sink for manual dishwashing in commercial kitchens. Regular sinks don’t provide the separation needed to prevent cross-contamination.

Q2: Do I need a separate hot water heater for the sink?

Not always—but your existing water heater must deliver 171°F to the sanitize compartment. Most residential heaters max out at 140°F. If yours can’t reach 171°F, you’ll need to install a dedicated commercial water heater or switch to chemical sanitizing.

Q3: Can I use bleach in the sanitize compartment?

Yes—but only if you follow strict ratios: 50–100 ppm chlorine (1 tablespoon of unscented bleach per 5 gallons of water). Always test with a chlorine test strip. And always use an air gap if you do.

Q4: How often should I clean the sink and drain lines?

Clean the sink surfaces daily with sanitizer. Drain lines should be flushed weekly with hot water and degreaser. Monthly: use a drain snake or enzymatic cleaner to break down grease buildup.

Q5: What if my kitchen has a dishwasher? Do I still need a 3-compartment sink?

Yes. OSHA and FDA require a manual backup sink in case the dishwasher breaks down. You can’t rely on machines during peak hours or power outages.

Q6: How much does it cost to plumb a 3-compartment sink?

• DIY (parts only): $300–$600 (sink, fittings, air gap, valves)
• Professional install: $1,200–$2,500
  But remember: A failed inspection can cost $5,000+ in fines and lost business. Investing upfront saves you more.

Final Thoughts: Your Sink Is Your Shield

Getting how to plumb a 3-compartment restaurant sink right isn’t about following rules—it’s about protecting your customers, your staff, and your livelihood. A properly installed sink prevents illness, passes inspections, and builds trust with your community.

You’ve done the work. Now, make sure your team knows how to use it:

• Train staff to wash, rinse, sanitize in order.
• Keep thermometers and sanitizer test strips visible.
• Log daily water temps (health inspectors love paperwork).

👉 Share this guide with your kitchen manager, fellow restaurant owners, or social media group. One post could prevent a shutdown.

Found this helpful?
✅ Pin it on Pinterest for your team
✅ Share on Facebook or LinkedIn
✅ Comment below with your biggest sink plumbing challenge—we’ll help!

Your kitchen’s safety starts with one sink. Make sure it’s done right.