How to Waterproof Electrical Cable

utility power lines in rain
  • 2 hours
  • Intermediate
  • 200
What You'll Need
Weatherproof electrical boxes
Sealing cable connectors
Wrench set
Cable ties (to make the drip loop)
Silicone rubber sealant
Plastic bottle
What You'll Need
Weatherproof electrical boxes
Sealing cable connectors
Wrench set
Cable ties (to make the drip loop)
Silicone rubber sealant
Plastic bottle

Water and electrical equipment don’t play well together, so if you want to protect your electrical cable from water damage, you’ll need to know the best way to waterproof it.

To waterproof an electrical cable, you have three available methods. You can waterproof electoral cables with liquid tape, with self-fusing silicone tape, or with a heat shrink tube.

Cable waterproofing includes work outside, on the roof, and indoors, closest to your electronic units.

Below are instructions on how you can best waterproof electrical cable, as well as a few key tools you will need to do the job right.

An adhesive-lined shrink tube is another good option for waterproofing your cables. This sticky tube heats up and shrinks around the wires, creating a tight seal.

For this method, you will need a heat gun, a regular blowdryer will likely not get hot enough.

1. Turn Off the Power

Whenever you work on electrical equipment, disconnect the power first. This is a basic safety precaution that helps prevent electrocution.

Even very seasoned electrical workers will tell you you need to turn the power off before you start working. It's always better safe than sorry.

If you don't know how to turn the power off, the process is pretty simple.

First, you need to locate the breaker box for your home. This is generally a silver box full of breakers that is located in an electrical room, maintenance closet, or garage.

All of the breakers in the box should be labeled so you know which breakers turn off power to which room.

Your breaker box should have a main breaker that will turn off the power to the entire house. If you cannot identify the best breaker to use to turn off power for your project, use this breaker.

Using this breaker will kill power to the entire house, though, so make sure that you keep an eye on appliances like your fridge and shut down your computer beforehand to avoid running into any issues.

If you don't want to turn off power to the entire home, look for the breaker specific to the part of the home you'll be working on and shut the power off there.

Test the power in the area by flipping your light switches or testing the plugs in the room and making sure that no power is available.

When you're done with your project, you can bring power back into the home using the same breakers, just flipping them the opposite way.

2. Select Your Sealing Method

You have three sealing methods available to you when it comes to waterproofing electrical wiring or cables.

You can use liquid electrical tape, you can use self-fusing silicone tape, and you can use adhesive-lined shrink tubing.

Liquid electrical tape can be purchased at a hardware store and is relatively inexpensive. It needs to be mixed well and then applied with a brush. We used an old paintbrush.

With liquid electrical tape, you need to apply it to the exposed area in thin, even coats—allowing ample dry time to elapse between each coat. We recommend at least twenty minutes.

The liquid tape can also be used to rejoin electrical wires that are exposed or not.

Self-fusing silicone tape works in a similar way. The self-fusing tape will wrap around the exposed wire and create a strong bond.

Follow the instructions on the self-fusing tape, and make sure you overlap the tape a good amount as you wrap it around the exposed wires.

Overlapping the tape will allow you to get a tight, secure waterproofing on your cable.

An adhesive-lined shrink tube is a great option for waterproofing electrical wires and cables. These tubes work really well and hold up to the elements outdoors.

To use adhesive-lined shrink tubes are really durable, but they do require the use of a heat gun to cure.

A regular blow dryer will not work, you need to use an actual heat gun to secure the shrinking tube to the cable.

Each brand of adhesive shrinking tubes will likely have slightly different instructions, so make sure to follow the instructions for your specific tube.

The same rule goes for any method of waterproofing that you use. Following the instructions for your specific method with exactness will be the most likely path to success.

3. Keep All of Your Connectors Tight

If you need to waterproof electrical cables connected to an outdoor electrical box, you need to take a few extra precautions and steps.

The connection between cables is essential for electrical health and effectiveness, so you need to make sure that the connection stays tight, sealed, and secure.

Using sealing connectors on all weatherproof electrical boxes, you can make sure connections stay tight. Hand-tighten the connectors first as tight as possible, after which a proper size wrench can be used to finish tightening them up to another 1/4 turn.

If you don't know where the connectors are located, look for a user manual or pay a visit to the internet and search for your specific make and model online.

4. Secure Electrical Cables in the Roof Area

This is another step where safety is critical.

After tightening your connectors, it's time to examine the grounding block, dish, and general cable entry area.

You want to make sure you are examining wherever it is not completely protected by the roof. There you can construct the cable into a rain loop (or drip loop) to prevent rain from hitching itself to the cable connectors or the dwelling’s inside.

If you are required to climb up a ladder to examine the underside of your roof, use safety and caution. We always recommend having a friend available to hold the ladder for you.

To form your cable into a rain loop after your examination of the area is complete, you'll need to secure your cables to the side of the home in loops.

The loop shape utilizes gravity to pull the water down, helping it run off the cables and avoiding water running down the cables to your electrical box.

If these outdoor cables are not waterproofed, use one of the methods discussed in part two to waterproof them before looping them.

You'll need a little extra length and slack in your cables to make sure looping is possible. We like to loop ours twice in two loops for optimal water runoff.

5. Waterproof Outside Connections

You can now use a 100 percent silicone sealant to coat your outside connections if you have not already used one of the previous methods discussed.

You can purchase this sealant at nearly every home improvement outlet, and it's a good option for when you need to cover larger, dimensional areas as opposed to straight wire or cable.

When you apply this sealant, coat only the outside. Never put sealant on the threads and assembly because you will then need to cut them off. You shouldn’t attempt this coating if it is raining or damp outside. Instead, wait for a dry day.

You'll likely need a few coats of sealant, but follow the instructions on the package for exact directions.

If you think these connections have been exposed to any kind of moisture, dry them with a hair dryer or let them dry on their own before you perform your sealing.

Also, use this sealant for the cable entry to the house. Applying sealant not only protects cables from water damage but also serves to prevent sun damage.

6. Protect the Switches

Now that you've taken care of your outdoor cables, it's important to make sure that the switches are protected too.

You can protect your switches with a simple plastic bottle.

Simply lop off the neck and attach it to the pole, with the bottle turned upside down and four holes punched into it for mounting the piece with tie wraps. Next, place the wired switch inside the bottle and use tie wraps to hold the bottle and switch in place.

This is a handy way to protect your switches and reuse some old plastic at the same time.

Once you've got everything protected from water damage, you can turn the power back on. We recommend checking on your waterproofing a few days later, and again about six months after.

You may need to retreat some aspects of the outdoor waterproofing as often as yearly, depending on the climate you live in, so make sure to regularly check on your cables.

Can I Waterproof My Electrical Cables on a Rainy Day?

No, you should never try to waterproof any outdoor electrical wire or cable on a rainy day. This is a recipe for disaster.

While you might notice that there's a problem with your outdoor cable waterproofing on a rainy day, you need to wait until the cable is completely dry to fix the problem.

In the meantime, we recommend you find a way to keep more water from getting into the cable by protecting it with a plastic cover or an umbrella.

It's a temporary solution that can hold you over till you can really fix the issue.

Do I Need to Replace My Electrical Cable After Water Damage?

Do you need to replace an electrical cable after water damage? Maybe.

Depending on how much water damage has actually happened, you may need to replace your outdoor electrical cable.

Sometimes cables can become submerged in water. When this happens for long periods of time, more than twenty hours, you will likely need to replace the cable.

If your cable has been well waterproofed, you may not need to replace it after it has been submerged, but if you haven't waterproofed your cables well, then you will likely need to replace them after water damage has been done.

If you have any questions about whether or not your cables need to be changed or replaced, always consult with a qualified electrician.

A Note on Electrical Safety

Being safe when working with anything electrical is critical. Electrocution can be very serious, even deadly.

Cutting safety corners may seem like it saves you time, but in the long run, you are jeopardizing your health and way of well-being when you ignore basic electrical safety.

Here are a few basic safety rules that will help keep you safe when you are working with anything electrical.

First, as we already mentioned, always cut the power when working with electrical wiring, or unplug electrical appliances before you work on them.

Recently a video of a TikTok DIY creator went viral when she tried to cut the cord on a lamp while it was still plugged in. Sparks flew in a big way and she way lucky to walk away with no major burns, electrical shocks, or fires.

Even when you're working with something as innocuous as a lamp, this anecdote illustrates how important it is to be safe and always work with electricity unplugged.

It's also important that you don't use or work with cords that have exposed wiring. That's shock or fire waiting to happen. If you need to replace damaged outlets or cords, do it.

The extra work is always worth your safety.

It's also important to keep a clear path to your circuit breaker or electrical panel. In the event of an emergency, you need easy access to these electrical panels.

If you've got a pile of boxes that have to move before you can open your breaker box, you could run into a problem that gets bigger before you have the chance to fix it.

Lastly, we always recommend learning the basics of electricity and home electrical before you begin working on anything.

Knowing a few simple basics can help you avoid issues before they ever actually become a problem. Knowing what materials are conductive, for example, can help you determine how not to solve an electrical problem around the home.

Similarly, it's smart to have a baseline for your home. If you know the voltage of your outlets on a good day, you can test them and quickly identify a problem when they malfunction.