Why Does Water Leakage Occurs In IP67 Underground Lights?

by Michael Hou | Post On: 9th-Oct, 2022

Why Does Water Leakage Occurs In IP67 Underground Lights

Many of us may notice that the so-called IP67 outdoor underground lights are with rainwater infiltrating into the fixture, even though they’re with IP test reports that prove they are waterproof and some of the lights are a good brand, there are still leaks.

So why does water leakage occurs In IP67 underground lights?

Before we give an answer, you have to understand what IP67 stands for. IP67 means the ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 m of submersion). For more info, please refer to this post: What is IP Rating (or Ingress Protection)?

The reasons for the water leakage of underground lights can be summed up as the following 4 situations:

  • Unreasonable design
  • Inferior material
  • Defective craftsmanship
  • Installation issue

Let’s go through why these 4 reasons can cause underground lamp leakage.

1. Unreasonable design

For example, some outdoor lamps are filled with glue to prevent the water from seeping in. These lamps sealed with glue meet the waterproof grade indeed when they leave the factory, and they will never leak.

However, if it is used in an outdoor environment for about half a year, the glue starts to age and turn yellow, under this circumstance the lamp will have a water leakage issue. Therefore, the design of Glue-filled waterproofing is unreliable, structural waterproofing is king. If a product design is unreasonable, it should not even exist.

There are also some lamps where the cover plate is not pressed firmly, and the manufacturer does not press a few more points. It should be known that underground lights are located in an environment that is eroded by water, it is easy to leak water if the cover plate is not compacted.

Take these inground lights as an example, there are only 2 screws for such a big lamp, and the screws are far apart. Do you think the cover can fix tightly to the lamp body? The cover plate will definitely warp up if it’s not compacted to the light body.

LED Underground Lights IP67

Several of the lamps mentioned above are not easy to pass the IP67 test. And even if it passes the IP67 grade test, it does not mean there will be no water leakage. Structural defects in lamps can also lead to water leakage.

The general test from manufacturers is they will perform a soak-in water test under certain temperature conditions, if there were no leaks after several hours of soaking, it is considered to have passed the IP67 testing.

RGB Inground Lights Waterproof Test

RGB Underwater Lights in Waterproof Testing

But the fact is, the use environment of outdoor lamps is complex in the actual working process. Unlike indoor lighting, underground lights get heated up when the sun shines and get cold when it rains. Thermal expansion and contraction – the air in the lamp will expand when the lamp is turned on, and the air will be compressed when the lamp is turned off, so the effect of such a cycle is called the breathing effect. The pressure ring of the lamp will be affected by the air pressure change caused by the breathing effect, thus the underground light will have water inflowed as a result.

Consequently, the lamps are unable to hold up to use due to their unreasonable structure design.

2. Inferior material

It’s the inferior lamp materials that contribute to its water leakage. Material quality is vital in preventing the water from inflowing inside the lamp. The waterproof nuts, sealants, silicon rings, etc., often perform well when installed, but they are not durable enough. The relatively poor silicone ring is aging in two months. And, if it’s often exposed to the sun, it will crack and water will enter. This is a premature failure and has not reached the designed life.

Accessories of Waterproof nuts, sealants, silicon rings for outdoor lighting used

Even though the silicone ring is not aged, if the silicone strip is not selected properly, it is not an inorganic material but an organic material that is likely to be affected by mold and decompose, and then result in leaking water.

Therefore, it’s very important to choose the right material with good quality.

3. Defective craftsmanship

For example, when assembling the lamp, the entire pressure ring of the lamp should be installed tightly in a proper range. As each screw has its fixed torque. If it is pressed too tightly, the rubber ring will be crushed. If it is pressed too loosely, the rubber ring will not be tight enough, so there will be a fixed torque.

Underground Light Structure and installation diagram

Companies with quality assurance have designed the torque, which can be in place in a good position with just a hit of the electric drill. Other companies without design and conditions to design the torque, just screwed it casually during assembly, it’s hard to not have water leakage issues.

Well, what if it is a well-known international brand, the lighting design is reasonable, and the materials are good quality, does the IP67 underground lamp will not have the leaking water issue?

The answer is NO!

If the inground lamp you use is from a famous supplier, but it still gets water leakage, the only possibility is improper installation methods.

4. Installation Method

Last but not least, the proper installation method is another guarantee to ensure the lamp is without a leaking problem. Generally, there are 3 improper installations that may cause this issue.

  • Installation is not smooth or even

The general possibility is that the installation is not smooth. One side is high and the other is low, plus there is often come with pressure from pedestrians or cars. Therefore, the position of the pressed rubber ring will lose its elasticity due to excessive pressure – and then it will leak.

  • IP67 is for short-term waterproofing

Secondly, if the drainage is not handled properly and the lamp is soaked in water for a long time, water leakage will occur. The IP67 of the inground light stands for short-term waterproofing. The lamp with an IP68 rating is the one that won’t leak after soaking in water for a long time, these lights are underwater lights or pool lights.

Install Condition of IP67 Underground Light

There should be enough space under the lamp, then there should be gravel and sand at the bottom, and at the lowest bottom, there’s a drain pipe. In this way, the water can be drained, and the lamp will not be soaked in water for a long time.

If the inground lamp is soaked in water for a long time, the environment is even worse than in the swimming pool. Because the ground is often cleaned with detergents such as oxalic acid, oxalic acid is corrosive and will invade the lamps and corrode the lamps, then it will eventually leak.

So, if the installation is smooth and there are drainage measures, will everything be fine and no water leakage anymore? It’s sad to know that the underground lamp may still have a leaking water issue.

  • Power supply wiring is not completely sealed

Another possible reason for the leak is the power supply wiring. Wiring with ordinary tape is actually not waterproof. Because the water vapor will enter the interior of the lamp through the gap of the tape wrapped around the wire, and the water mist is formed inside the lamp.

Therefore, the best way to avoid this would be to use a waterproof junction box. The junction box is filled with soft glue, the soft glue junction box sinks the wire ends to the ground, and the casing is well set. As a result, the water vapor won’t be able to get in.

Use waterproof junction box for wiring for IP67 outdoor lights

Use a waterproof junction box for wiring for IP67 outdoor lights. (Photos from: https://www.filoform.com/filobox-pu)

There are also many inground lamps that will leave two waterproof male and female sockets, you may think it would be waterproof if you screw it on. But actually, it’s not waterproof!

In fact, due to human factors such as tolerances in the production of male and female plugs and the quality of the plugs, water can still inflow from the gaps. The safe way is to wrap more tape on the outside of the male and female plugs and put silicone glue on it, which is double insurance.


Overall, the water leakage issue that occurs in IP67 underground lights is either poor quality of the lamp or improper installation. Find out why underground lights leak, you should then be able to get how to deal with the leakage of outdoor lights. Penglight is a professionally led light sourcing agent, we specialize in many outdoor lights, such as underground lights, swimming pool lights, step lights, etc. If you need a professional sourcing company to help you handle the lighting products, feel free to contact us.

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