Is Solderstick Waterproof? IP67 Wire Connectors Explained

If you're joining wires under a ute tray, inside a boat's bilge or along a caravan chassis rail, the first question is simple: are solder seal connectors waterproof? The short version is yes, when they're installed properly. A Solderstick is a solder seal connector: it joins the wire with solder and seals both ends with adhesive, so water has no path into the joint.

The longer version matters, because "waterproof" is a loose word and an IP rating is a precise one. Solderstick connectors carry an IP67 rating, which means something specific: dust tight, and protected against temporary immersion in water. It does not mean the join will survive anything you throw at it forever.

This guide explains what the IP code actually says under IEC 60529, what IP67 does and doesn't cover, how to get a reliable seal every time, and when it's worth adding a length of dual wall heat shrink over the top.

Quick answer

• Solderstick connectors are rated IP67: dust tight and protected against temporary immersion in water.
• Under IEC 60529, the immersion test (the "7") is up to 1 metre of water for 30 minutes. It is not a rating for continuous submersion, pressure washing or high-pressure jets.
• The seal only works if the wire size suits the connector, the strip length is right and the adhesive rings fully melt and grip the insulation.
• For joins that sit in water, get hosed or pressure washed, rub on chassis edges or flex a lot, add adhesive-lined dual wall heat shrink over the connector.

What makes Solderstick connectors waterproof?

A Solderstick connector is a short piece of clear polyolefin heat shrink tube with three parts inside. In the centre is a ring of low-temperature solder. At each end is a coloured sealing ring made of heat-activated adhesive. The tube itself shrinks when heated.

When you heat it, three things happen at once:

1. The solder ring melts and flows into the stripped strands, making the electrical join.
2. The tube shrinks down tightly around the wire.
3. The adhesive rings melt and flow between the tube and the wire insulation, bonding the two and sealing each end.

The adhesive is what makes Solderstick connectors waterproof. A plain heat shrink tube grips the wire, but water can still creep along the tiny gap between tube and insulation. Melted adhesive fills that gap. Because the tube is clear, you can see whether the solder has flowed and whether the adhesive has squeezed out at each end, which is the best visual check you have.

For a deeper look at how they're built, see What Is a Solderstick?.

IP codes explained: what IEC 60529 actually says

IP stands for International Protection (often called Ingress Protection). The system is defined in the international standard IEC 60529, published in Australia as AS 60529. It rates how well an enclosure keeps out solid objects and water, using two digits after the letters IP.

• The first digit (0 to 6) covers solid objects, from fingers and tools down to fine dust. It also covers protection of people from touching hazardous parts inside.
• The second digit (0 to 9) covers water, from dripping through to immersion and high-pressure spray.
• An X in place of a digit means that property wasn't rated. IPX7 means tested for immersion, with no dust rating claimed. It doesn't mean zero protection.

First digit: solids and dust

The dust tests for 5 and 6 are run in a chamber that keeps fine talcum powder suspended in the air, typically for 8 hours.

Second digit: water

You'll also see IP69K on vehicle parts. That comes from the road vehicle standard ISO 20653 and covers similar high-pressure, high-temperature cleaning. For more background on ratings for outdoor and marine gear, read IP Rating Explained: Securing Your Outdoor and Marine Gear.

What IP67 means for Solderstick connectors

Read the two digits separately and IP67 is easy to decode:

• 6: dust tight. No dust gets in. On a 4x4 doing corrugated roads, that matters as much as water, because fine bulldust packed with moisture is what eats unprotected joins.
• 7: temporary immersion. The test immerses the item to a depth of up to 1 metre for 30 minutes, and it passes if water doesn't get in in harmful amounts.

In practice, an IP67 connector suits joins that get rained on, splashed with road spray, sit in a puddle for a while, or go under during a creek crossing. That covers most 12V and 24V wiring on a vehicle, trailer, caravan or boat above the waterline.

So, are Solderstick connectors waterproof to IP67 straight out of the bag? Not quite. The rating describes a correctly installed connector. A connector on the wrong size wire, or one where the adhesive never fully melted, won't seal to that standard. The rest of this guide is about making sure yours does.

What IP67 doesn't mean

IP ratings are lab tests under fixed conditions. Here's what IP67 does not promise:

It isn't a rating for permanent submersion

The 7 is for temporary immersion. Joins that live underwater, such as a bilge pump lead lying in bilge water or a pond pump cable, are outside what the test covers. For those, add dual wall heat shrink over the top and, better still, keep joins above the water line.

It doesn't automatically include water jets

The water digits 1 to 6 build on each other, but 7 and 8 are a separate category. IEC 60529 treats a 7 or 8 rating as not covering water jets unless the product is also tested and marked for them, which is why you see dual markings like IP66/IP67. A join under the wheel arch that cops the pressure washer every trip needs extra protection.

It isn't a salt water, chemical or UV rating

The immersion test uses water under lab conditions. IP codes don't rate resistance to salt, fuel, oil, battery acid or years of Australian sun. Those depend on the materials and on keeping the join covered and out of direct sun where you can.

It doesn't cover the rest of the circuit

The connector seals the join. It can't stop water that gets in somewhere else. If a plug, switch or lamp at one end of the circuit lets water in, the water can travel along the strands inside the insulation. The join stays dry, but the wire next to it corrodes. Seal the whole circuit, not just the splice.

How to get a waterproof seal every time

Most failed joins come down to one of five things. Get these right and your Solderstick connectors will be waterproof to the IP67 standard they're rated for.

1. Match the connector to the wire

The adhesive can only seal a gap it can fill. Too thin a wire in too big a connector leaves a gap; too thick a wire won't fit or won't let the tube recover. Use the size chart:

If you're unsure of your wire size, check Solderstick Sizes: Colour Chart and Which Wire Each Fits. A connector doesn't fix undersized cable, so size the cable and fuse for the load first. For battery cables and anything heavier than 6mm2, use crimped or soldered lugs rather than a splice connector.

2. Strip the right length

Strip only enough so the bare strands sit under the solder ring and the insulation sits under each adhesive ring. If you strip too far, bare copper sits under the adhesive and the seal grips metal instead of insulation. Hold the connector against the wire before you strip to judge the length.

3. Start with clean, dry wire

Adhesive won't bond well to insulation coated in grease, dirt or water. Wipe the insulation clean and dry it before you start. If the copper is dark or green, cut back to bright strands.

4. Use a heat gun and heat evenly

A heat gun is the recommended heat source. Work from the centre outwards: melt the solder first, then move to each end so the tube shrinks and the adhesive rings flow. A lighter or torch can scorch the tube and is a last resort only. Always work with the circuit isolated and the battery negative disconnected.

5. Check, then let it cool

Look through the clear tube. You want solder that has flowed into the strands rather than sitting as a ring, a tube that has shrunk tight along its length, and a small bead of melted adhesive at each end. Let the join cool before you move or bend it, because the solder and adhesive are still soft while hot.

For the full step-by-step method, see How to Use Solderstick Wire Connectors.

Signs a Solderstick connector hasn't sealed

• The coloured adhesive rings still look like rings rather than a melted band, with no bead at the ends.
• The tube is loose at one end, or you can see an air gap between tube and insulation.
• The solder ring is still visible as a ring, or has run to one side and missed the strands.
• The tube is brown, blistered or split from too much heat.
• Bare copper shows beyond the end of the tube.

If you see any of these, cut the join out and do it again. A second blast of heat sometimes finishes a seal that's nearly there, but a scorched or split tube should always be replaced.

When to add dual wall heat shrink over the connector

For most joins, Solderstick connectors are waterproof enough on their own. Add adhesive-lined dual wall heat shrink over the top when the join faces conditions the IP67 test doesn't cover:

• Underwater or regularly wet: bilge areas, joins below a boat's waterline, pond and garden pump leads.
• Pressure washing: wheel arches, underbody and trailer wiring that gets hosed after every beach or mud trip.
• Abrasion: joins near chassis rails, spring hangers or anywhere they can rub. A thicker outer layer takes the wear instead of the connector.
• Flex and vibration: a longer outer sleeve spreads the bend away from the join, so the wire doesn't fatigue right at the edge of the connector.
• Sun exposure: joins on roof racks, solar panel leads and boat T-tops.
• Multi-core cable: after joining the individual cores, a larger tube over the outer sheath seals the whole cable and stops water getting in between the cores.

How to size the outer sleeve

Pick a tube that slides easily over the finished connector, and whose fully shrunk size is smaller than the wire or sheath it needs to grip. Cut it long enough to reach well past each end of the connector onto the insulation. As a rule of thumb, at least 10mm of overlap onto the insulation at each end gives the adhesive enough length to seal. Slide the tube onto the wire before you make the join, because you can't get it on afterwards.

For more on ratios and sizing, see Heat Shrink Ratios Explained.

Waterproof Solderstick connectors vs other wire joins

How does a Solderstick compare with the other common ways to join wire when water is involved?

Which should you use?

• If you're wiring trailer lights or a caravan's 12V circuits that see rain and road spray, use a waterproof Solderstick connector on its own, sized to the wire.
• If you're wiring a 4x4 that does creek crossings and gets pressure washed, use a connector plus a dual wall heat shrink sleeve over joins under the vehicle.
• If you're wiring a boat, use Solderstick connectors above the waterline and add dual wall heat shrink over any join in the bilge or exposed to spray.
• If you're joining multi-core cable, join each core with its own connector, stagger the joins, then seal the sheath with a larger dual wall tube.
• If you're working on battery cables or anything heavier than 6mm2, use crimped or soldered lugs, not splice connectors.
• If the wiring is 230/240V mains, stop. Solderstick connectors are for low-voltage work only, and fixed mains wiring in Australia must be done by a licensed electrician.

Frequently asked questions

Are solder seal connectors waterproof?

Yes, when installed correctly. The adhesive rings at each end melt and seal the tube to the insulation, and Solderstick connectors are rated IP67. That covers temporary immersion, not permanent submersion or pressure washing.

What does IP67 mean?

IP67 means dust tight (6) and protected against temporary immersion in water (7). Under IEC 60529, the immersion test is up to 1 metre deep for 30 minutes.

Is IP67 better than IP68?

IP68 covers continuous immersion beyond the IP67 test, but the depth and time are set by the manufacturer, so you need to check what each IP68 product was tested to. For wiring joins above the waterline, IP67 is what most people need.

Can Solderstick connectors be used underwater?

The IP67 rating covers temporary immersion only. For joins that sit in water permanently, add adhesive-lined dual wall heat shrink over the connector and keep joins above the water where you can.

Are Solderstick connectors OK in salt water?

IP codes don't rate salt water resistance. A properly sealed join keeps salt water away from the copper, but on boats add dual wall heat shrink in wet areas and rinse gear with fresh water after use.

Why did my Solderstick connector leak?

The usual causes are a connector too large for the wire, stripping too much insulation, dirty or wet insulation, or not enough heat on the ends to melt the adhesive rings. Check for a bead of adhesive at each end and redo any join without one.

Can I use Solderstick connectors on 240V wiring?

No. Solderstick connectors are for low-voltage work such as 12V and 24V automotive, marine, caravan, solar DC and garden lighting. Fixed 230/240V wiring in Australia must be done by a licensed electrician.

What to use

For most 12V and 24V jobs, an assorted kit covers every wire size from 0.25mm2 to 6.0mm2. The 100PCS kit (25 white, 35 red, 30 blue, 10 yellow) suits a home workshop, while the 250PCS kit suits bigger projects such as a full caravan or 4x4 fit-out. If you use one size a lot, the bulk 100 packs give you 100 of one colour.

For joins that need extra protection, add adhesive-lined dual wall tube from the heat shrink range, or grab the Ultimate Heat Shrink Bundle to cover the full range of sizes. Every order ships free by Express Australia Post anywhere in Australia, and orders placed by 1pm are dispatched the same day.