Liquid water inside Ethernet cables is the bane - even direct-buried Ethernet cables with waterproof tape offer only a limited degree of protection. If the rugged cable jacket is compromised, waterproof tape can mitigate the problem, but there will still be measurable consequences. Why? Waterproof tape is designed to activate in the presence of water and produce a gel that is inherently somewhat conductive. See Direct Burial Ethernet Cables: Gel Filling vs. Waterproof Tape for a neat experiment I conducted that illustrates this point.
This got me investigating further. Can Ethernet cables with waterproof tape get wet? Is water-activated gel harmful to data transmission? Does the signal attenuate? How much worse would liquid water be in the same situation? Of course, I had to run more experiments to find out!
So, what exactly happens to Ethernet cables when water gets inside?
I like to do "what if" experiments, so I got the following:
Cat6 Shielded Riser Bulk Ethernet Cable, 213 feet long
Cat6 Unshielded Direct Burial Bulk Ethernet Cable, 180 feet long
...a bucket with water
Both cables terminated from keystone jack to keystone jack, called a permanent link configuration. What is a permanent link? See What is an Ethernet patch cord? The ANSI/TIA permanent link test is pretty rigorous, and the Fluke DSX-8000 provides more diagnostic data when running such a test. This is exactly what I was looking for.
I took my cutting and stripping tools and opened the cable jackets on both cables, about halfway through the length. I then ran the Fluke test as follows:
Immediately after termination (to make sure the cable is intact, to set a baseline)
Immediately after breaking the cable jacket, to make sure the cable was not damaged
After being submerged in the bucket of water, and periodically
The goal was to show how quickly a cable could fail, and if it did fail, how severe the failure would really be. Believe it or not, there are different degrees of failure.
Indoor Cable Fails Seriously
Oops. Not at all. As expected, the indoor cable failed severely immediately after it entered the water. Two hours later, it not only failed the ANSI/TIA Cat6 Permanent Link + PoE test, but it also failed the 5GBASE-T + PoE bandwidth test. This cable is completely dead, by the way. Anyone need a clothesline?
So, what does the waterproof tape buy you? After two hours, the CMX jacketed Cat6 outdoor cable still passed the ANSI/TIA Cat6 Permanent Link + PoE test, but after eight hours the waterproof tape absorbed enough water to cause that test to fail. What is unique, however, is that the bandwidth test kept passing. In fact, multiple bandwidth tests were run over a 24-hour period with both 5 Gigabit and PoE. All tests passed, and kept passing, with no noticeable additional performance degradation. The results are impressive compared to the riser-rated cable, which failed immediately.
This shows that there are multiple degrees of "failure." Failing the stringent ANSI/TIA tests does not necessarily mean data cannot be delivered.
In order from least stringent to most stringent, here are the various ways to test Ethernet cables:
Verification (finds shorts and wiring errors, not performance related)
Qualification (bandwidth or speed test of 1 Gigabit or higher, the minimum requirement for the cable to perform as expected)
Certification (measures cable performance using electrical metrics, providing a built-in safety factor to ensure the network will work under any conditions)
Usually, unless you are installing a complex network and have higher-end needs, you will not start to notice a problem until the speed tests start failing. If the verification test fails, you will definitely notice because your cable simply will not work.