Why Romex Fails on Docks in Naples | CoHarbor Electric

Why Romex Fails on Docks in Naples

We’ve lost count of how many times we’ve seen it — you walk down a beautiful dock in Naples, everything looks fine on the surface, but tucked underneath the decking or inside a weathered junction box, there’s regular Romex cable running through conduit. It’s stiff, discolored, maybe a little swollen from moisture, and the copper inside is already turning black.

Nine times out of ten, that same homeowner will tell us, “It’s worked fine for years.” And sure — until it doesn’t.

At Coharbor Electric, we’ve seen more dock and lift failures caused by Romex than anything else. It’s one of those shortcuts that seems harmless at first but ends up costing you more in the long run — not just in repairs, but in safety risks.

Let’s talk about why Romex fails so quickly on coastal docks, what’s really happening inside that cable, and what we do instead to make sure a dock wiring system in Naples actually lasts.

What Romex Is — and What It’s Not

Romex (technically NM cable, short for nonmetallic-sheathed cable) is great — for indoor use. It’s easy to pull, inexpensive, and perfect for dry locations like inside walls, attics, and ceilings. That’s what it’s made for.

What it’s not made for is moisture. The “NM” in its name literally means “nonmetallic,” but it also means “non-moisture resistant.” The outer sheath isn’t sealed against humidity or UV light, and the insulation on the wires inside breaks down fast when exposed to damp air, condensation, or salt.

If you look closely at a Romex jacket after a couple of seasons near the coast, you’ll see small cracks where it’s been flexed or heated. Those cracks let moisture in — and that’s the beginning of the end.

The Naples Factor: Salt, Sun, and Humidity

If Romex struggles in a damp basement, imagine what it goes through on a dock in Naples. Between the salt air, year-round humidity, and the constant baking sun, it doesn’t stand a chance.

Here’s how it breaks down:

1. UV Exposure – The sun dries out and cracks the outer jacket, especially the white or yellow plastic used on Romex. Once that happens, the insulation inside starts to fail.

2. Moisture Intrusion – Salt air finds its way in through every crack, screw hole, and conduit opening. Even if the cable looks dry, moisture is creeping inside.

3. Corrosion – The copper inside Romex isn’t tinned or coated. It starts to oxidize immediately in salty air. Over time, it turns dark brown, then black, becoming brittle and resistive.

4. Heat and Load Stress – As corrosion increases resistance, the wire starts to heat up under load. That extra heat accelerates the breakdown — a bad cycle that ends with tripped breakers, melted insulation, or worse.

We’ve pulled Romex out of Naples docks that was literally crumbling apart in our hands after just five years. That same job done with marine-grade wire could’ve lasted twenty.

“But It’s in Conduit!” — The Biggest Misconception

We hear this a lot: “It’s okay, I ran it in PVC conduit.”

Here’s the problem — conduit doesn’t keep moisture out. It traps it in.

Every piece of conduit near water eventually fills with condensation. The temperature difference between day and night pulls moisture in through fittings, especially around docks where it’s humid 24/7. The result? That conduit becomes a little water pipe with your Romex sitting right in it.

Romex isn’t rated for that environment. Once the jacket absorbs moisture, the copper inside starts oxidizing, the insulation softens, and eventually the ground wire starts to break down first. That’s usually when the first sign appears — tripping breakers or that faint burning smell near the panel.

Why It’s Against Code

The National Electrical Code (NEC) is very clear: Romex (NM cable) cannot be used in wet or damp locations — and docks are both.

Even if you’re not directly over water, if the wiring runs through conduit that can collect condensation or sits outdoors, it’s considered a wet location. That makes Romex off-limits.

Inspectors know this rule by heart. If a Naples dock has Romex anywhere in its wiring system, it’ll fail inspection on the spot. But beyond passing code, this rule exists because of real-world safety concerns. The longer that cable sits in moisture, the more likely it is to cause arcing, corrosion, or shorts — and on a dock, that can mean current leaking into the water.

What Happens When Romex Fails

We’ve seen all kinds of failure points from Romex on docks. Here’s what typically happens over time:

• Cracked Insulation – Exposes live conductors to moisture and the metal conduit.

• Corroded Ground Wires – Once the ground fails, GFCIs may stop tripping correctly.

• High Resistance and Heat Buildup – The wire starts cooking itself from the inside.

• Intermittent Power – Lift motors slow down, lights flicker, breakers trip randomly.

• Shock Hazards – The worst-case scenario. Current finds a path through metal frames or even the water.

It’s not just an inconvenience — it’s a serious hazard.

We once inspected a dock where the owner said, “It’s been running fine for years.” Sure enough, the lift worked — until we tested voltage on the metal frame. It read 22 volts. That’s stray current leaking through corroded Romex insulation into the lift’s housing. Thankfully, nobody had gotten in the water near it.

The Right Way to Wire a Dock

If you want a system that lasts, you’ve got to start with the right materials.

Here’s what we use on every marine job in Naples:

1. Tinned Copper Wire (Marine Grade)
   Every strand is coated to resist salt corrosion. It stays flexible, even after years of exposure.

2. Liquid-Tight Flexible Conduit
   Rated for UV and moisture, and properly sealed with gasketed fittings.

3. Heat-Shrink Connectors
   Crimped and sealed to keep out moisture completely.

4. Marine-Rated Junction Boxes
   With gaskets, stainless hardware, and drain holes for condensation.

5. GFCI and GFPE Protection
   Installed at the panel and load points to instantly trip if current starts leaking.

Every connection, every crimp, every screw gets coated with dielectric grease or corrosion inhibitor. It takes a little longer, but it’s the difference between a system that lasts two years and one that lasts twenty.

The Cost Difference

We get it — Romex is cheap and easy. Marine wire isn’t. But here’s the truth: you’re not saving money when you cut corners on dock wiring.

A 100-foot run of Romex might cost $50. The same run in tinned marine wire could cost $120–150. But if you have to replace that Romex every five years — and pay for labor each time — you’ve spent triple what you would’ve if you’d done it right the first time.

And that’s not even counting the potential cost of a damaged lift motor, a tripped breaker that won’t reset, or corrosion that ruins your panel.

Real-World Example from the Field

We were called to a Naples property where the boat lift had stopped working after a heavy rain. The owner thought it was the motor.

When we opened the junction box, the inside looked like a science experiment — green corrosion, flaking insulation, and blackened copper. The entire run was standard Romex, pulled through PVC conduit that had filled with condensation.

The insulation crumbled as we pulled it out. The copper wire snapped like pencil lead.

We rewired the whole lift with marine-grade wire, sealed connectors, and proper bonding. The lift ran smoother and faster, and it’s still working perfectly today — three years later, no corrosion, no issues.

That homeowner now calls us once a year for a quick dock inspection. Smart move.

How to Tell If Your Dock Has Romex

You can usually spot it without opening anything:

• If you see a white or yellow flat cable entering conduit near the panel, it’s Romex.

• If the cable feels stiff, chalky, or brittle, it’s already breaking down.

• Look for small cracks where the insulation enters the box.

• If your dock wiring hasn’t been touched in over 10 years, it’s worth checking — older systems used Romex routinely before the code updates.

If you’re not sure, we can do a quick inspection and tell you in minutes.

Why We Don’t Cut Corners

We’ve built our name on doing coastal electrical work the right way. There’s no room for shortcuts when it comes to safety near water. We’d rather walk away from a job than use materials we know will fail.

We don’t just follow code — we build beyond it. That’s how we keep our customers’ docks and lifts running safely for the long haul.

Final Thoughts

Romex has its place, but that place isn’t anywhere near saltwater. It breaks down fast, hides corrosion inside, and turns a simple dock circuit into a safety hazard waiting to happen.

At Coharbor Electric, we’ve rewired dozens of Naples docks where Romex had failed, and every time, the homeowner said the same thing: “I wish I’d known.”

If you’ve got a dock or boat lift that hasn’t been inspected in a while, or if you suspect the wiring isn’t marine-grade, don’t wait for it to fail. Let’s take a look, test your circuits, and make sure your system’s built to handle our coastal environment — safely and properly.

⚡ Call Coharbor Electric today to schedule a dock wiring inspection or rewire consultation. We’ll make sure your system meets code, resists corrosion, and keeps you safe on the water — year after year.