Can outdoor extension cables be run through standing water?

Question

I'm looking to hook up decorations in the lawn, but to get power to them without causing a tripping hazard (running it across the front entrance), I need to run it a ways and part of the way is a place that usually gets some standing water when it rains. Is it fine for some grade of extension cable (W) to run thru water if undamaged, and away from the connectors?

The IEWC Portable Cord Guide describes some classifications for extension cords:

Category	Letter Code	Definition
Service	S	Severe Service (600V)
	SJ	Junior Service (300V)
Jacket	E	Elastomer
	T	Thermoplastic (Unless first letter of code - then it designates tinsel cord)
	O	Oil resistant jacket
	OO	Oil resistant jacket and insulation
Weather Resistance	W	Weather resistant
Application	V	Vacuum cord

Looking up most information about extension cords just says "no water!"

• "Never allow an extension cord to run through snow or standing water"
• "Do not [...] allow them to run through water or snow on the ground."

However, there's UF-B wire that exists and if able to be direct buried, must be able to withstand sopping wet earth all around. Could I make an extension cord running UF-B to a junction box with plugs and an extra-duty cover on it?

Answer 1

Direct bury cable is meant to be put in the ground and then left. Being buried then protects it from damage.

If you are using it as an extension cord laying on the ground then it will be subject to damage from people stepping on it or critters messing with it.

Actual gardening extension cords (the type that the manufacturer expects people to drag through puddles) are expected to be a temporary connection and inspected before every use. They are not meant to be left completely unattended.

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If you don't mind putting in a more permanent installation you can actually bury most of the run or run it above the front entrance. Either using appropriate cables of course.

Answer 2

GFCI

No matter how good the extension cord is, and the better ones should be able to handle at least some water around them, this is one of the top use cases for a functioning Ground Fault Circuit Interrupter (GFCI).

You may start with a perfect extension cord - no problem at all as long as the ends are not in water. But outside = critters. And critters = insulation damage. Enough insulation damage (the outer covering and then the insulation on the actual wires) and you will probably not have a short circuit (overcurrent trip) but will run a serious risk of a ground fault. Which could easily take the form of:

• Your extension cord is plugged in and lights are plugged in and turned on
• You are working on adjusting the lights or something else in the yard next to the wet extension cord (does not have to be totally covered with water to be a hazard if damaged)
• You drop a tool or a screw or something and reach down to the wet area next to the extension cord
• Zap!

A properly functioning GFCI will protect you from most such situations (no guarantees in this world). You still should be vigilant - always check your extension cords when setting them up for the season and repair (of outer covering is a little messed up) or replace (if it is a lot messed up, particularly if you can see the actual copper wires exposed). But this will protect from a lot of problems that could be dangerous, even fatal, without a GFCI.

GFCI is required for outside receptacles. But in an older house, or if you run the cord through a window to an inside receptacle even on a newer house, it might not be protected. GFCI can be installed as part of a receptacle (extremely common for kitchen and bathroom, can be easily retrofitted unless the receptacle is in a very small box) or separately ("deadfront") or together with a breaker (more expensive but has certain advantages).