Gel Filled Cable – Water blocking 101

Cable jackets are not water blocking by default. Most jacket materials (PVC, Polyethylene, etc.) are water resistant. More specifically, they can get wet, dry out, and the cable in them will most likely continue to perform well. That mainly depends on the length of the time spent in water and the exposure.

A cable submerged in water and an indoor cable will require different level of water blocking in order to assure performance. Given enough time, water will get through anything. A PVC (polyvinyl chloride) jacket (most common cable jacket) has weeks to a few months before failing if located underwater. A PE (polyethylene) jacket is dramatically more water resistant and may last many months, even years. For long term water blocking, it is best to use a cable with a water blocking layer.

When looking at water blocking options for a cable that will be submerged in water for long periods of time, there are two options to choose from, dry water blocking, and gel water blocking.

Dry water blocking

Dry water blocking provides an additional layer in the cable. The extra layer is an impregnated cloth that is placed under the jacket and above everything else. If the jacket is punctured, the water reaches the cloth and causes it to swell and block the water. Since it is only a cloth layer, performance is not affected, nor is cable termination. The extra cloth layer is simply cut off in order to plug a connector on.

Gel Filled water blocking

While dry water blocking will double or triple the lifespan of a cable underwater – gel water blocking is the ultimate solution for water blocking. The gel is added to a braid shield or extruded on top of a foil shield. The gel fills in any gaps by the nature of the material.
It may take some getting used to terminating a gel filled cable. after stripping the cable, the gel needs to be wiped before plugging the connector. The gel can be removed with alcohol or citrus wipes designed for this purpose.

Fire rating and cable termination

Water blocking cable jackets lack fire rating. According to the NEC code, you can go 50 ft. into a building with unrated cable before you have to change to a fire rated cable (CM, riser, plenum etc.). this means you will either have to terminate this cable by 50 ft. or change it at that distance.
Connectors used on the cable’s ends must comply with the use – use outdoor connectors for use outdoor, etc.