Okay, let's break down the code requirements for GFCI protection around sinks and address your specific scenario.

Relevant Code Sections (U.S. - Based on NEC)

The primary code section governing GFCI protection around sinks in dwelling units is: NEC 210.8(A): Dwelling Units. This section lists locations where GFCI protection is required in dwelling units. Sinks are specifically addressed within this general section. 210.8(A)(7) Bathrooms - Receptacles installed in bathrooms 210.8(A)(9) Sinks - where receptacles are installed within 6ft of the outside edge of the sink 210.8(A)(10) Kitchens - Receptacles that serve countertop surfacesKey Considerations and Interpretations1. GFCI Protection Requirement

The NEC requires GFCI protection for receptacles installed within a specific proximity to sinks. The most common interpretations is 6 feet from the outside edge of the sink.2.

How GFCI Protection is Achieved

GFCI protection can be provided in several ways:

GFCI Receptacle

Installing a GFCI receptacle at the location where protection is needed.

GFCI Circuit Breaker

Using a GFCI circuit breaker to protect the entire circuit that feeds the receptacles near the sink.

Feed-Through GFCI Receptacle

Installing a GFCI receptacle upstream (before) the other receptacles on the same circuit. The "load" terminals of the GFCI receptacle are then used to feed power to the downstream receptacles, providing them with GFCI protection.3.

"One Protects All" Principle

The NEC does allow a single GFCI device (either a receptacle or a breaker) to protect multiple receptacles on the same circuit. This is where your "one protects all" idea comes from. However, this only applies if the non-GFCI receptacles are wired downstream of the GFCI receptacle or breaker on the same circuit.

Analyzing Your Specific Situation

Let's apply the code to your situation: Two Receptacles (Stacked) on Left Side of Sink

One is a GFCI. One is not a GFCI (but is on the same circuit as the GFCI above it).

Analysis

If the non-GFCI receptacle is wired downstream of the GFCI receptacle (using the load terminals), then it is protected by the GFCI receptacle. This is permissible. However, it must be wired correctly for the GFCI to protect the downstream receptacle. If it is not wired on the load side of the GFCI, then it is a code violation.

Quad Receptacle on Right Side of Sink

It is a GFCI receptacle. It is on a different circuit than the receptacles on the left.

Analysis

This receptacle independently provides GFCI protection for anything plugged into it. Because it is on a different circuit, it does not provide GFCI protection to the receptacles on the left side of the sink.

Determining Code Compliance

To determine if your setup is code-compliant, you must determine the following:1. Distance

Are all of the receptacles within 6 feet of the outside edge of the sink? If any receptacles are outside this zone, they do not require GFCI protection.2.

Wiring of the Stacked Receptacles

Is the non-GFCI receptacle on the left wired on the "load" side of the GFCI receptacle above it? If so, it is protected. If not, it is a code violation. A qualified electrician can easily test this.

Possible Code Violation The most likely code violation is that the non-GFCI receptacle on the left is NOT GFCI protected. Unless it's physically outside the 6ft radius of the sink, it needs to be GFCi protected, either by being wired properly to the load side of the above GFCi, or swapped for a GFCI receptacle.

Recommendations1. Consult a Qualified Electrician

The safest and most reliable way to ensure code compliance is to have a licensed and experienced electrician evaluate your wiring. They can perform the necessary tests to verify GFCI protection and identify any potential hazards or code violations.2.

GFCI Tester

You can use a GFCI tester (available at most hardware stores) to partially verify that the GFCI receptacles are functioning correctly. The tester will simulate a ground fault and should cause the GFCI to trip. However, this test does NOT guarantee that the downstream receptacles are properly protected if wired to the load side, only that the GFCI receptacle itself is working.

In Summary

While it's possible that your setup is code-compliant if the non-GFCI receptacle is wired correctly downstream of the GFCI on the same circuit, you must verify this with testing or, ideally, a professional electrician. The existence of a GFCI receptacle on a different circuit does not provide GFCI protection to receptacles on other circuits. Flag for review