Mercury Wire Offers Water Blocking Technologies
What Is Water Blocking in a Cable?
Water blocking is any construction that stops water from traveling along the inside of a cable. A jacket alone does not do this: if the jacket is breached at one point, moisture can wick the full length through the interstitial spaces between conductors. Water blocking fills or seals those spaces so a single breach stays local instead of flooding the run.
| Method | How it works | Best for | Trade-off |
|---|---|---|---|
| Dry (swellable tape or yarn) | Water-swellable material expands on contact with moisture to block travel along the cable | Cleaner terminations and frequent field handling; lighter cable | Material cost can be higher than gel |
| Gel-filled | A water-blocking compound fills the interstitial spaces inside the cable | Continuous submersion and maximum moisture exclusion | Messier to strip and terminate; adds weight |
A common misconception is that all jacketed cables are water-resistant by default. The fact is that while an outer jacket adds some protection against moisture reaching internal conductors, it does not make them waterproof. That’s why understanding the environmental conditions wire and cable will be exposed to is among several of the key factors to consider during the design and construction of your wire and cable solution.
Depending on the frequency and exposure to moisture, the appropriate level of water resistance can be achieved through the careful selection of both materials and the specific construction of your wire and cable. For example, in cases where a cable is occasionally exposed to moisture, using Polyethylene (PE) instead of Polyvinyl Chloride (PVC) may be enough to avoid cable degradation. However, in instances where a cable is expected to sit in standing water for indefinite periods of time or is intended for use in aquatic applications, a more robust water-resistant solution may be required.
Water blocking technology is an approach through which additional material (tape or a gel) is added to a cable’s construction to fill the interstitial areas. When used with suitable connectors and proper termination, water blocking can be effective in mitigating water and moisture. Mercury Wire offers two water blocking technologies. These include dry water blocking and gel water blocking. Here’s how they work:
Dry water blocking
Dry water blocking involves the use of special tapes that are carefully wrapped around the cables internal component and sits right beneath the cable’s outer jacket. If the outer jacket is punctured, the tape’s absorbent side will expand upon contact with the water and fill the puncture site – thereby helping to block water from seeping into the cable. The tapes themselves are typically treated with chemical technology that causes the water absorbed to gel or solidify, which make them less likely to migrate. Using dry water-blocking technology has been estimated double or triple the lifespan of a cable used in wet environments. Mercury Wire recommends the use of dry water-blocking for high moisture environments where the cable is not continuously exposed to water.
Gel filled water blocking
Gel water blocking involves the careful application of water-repelling gel to a cable’s shield to help stop the longitudinal migration of water. During the manufacturing process, the gel is carefully applied to fill-in gaps within the cables internal conductors. Once the final, outer jacket is applied, and having filled-in all internal gaps, the migration of water through the cable is less likely. Mercury Wire recommends the use of gel water blocking technology as part of a comprehensive design including proper termination and selection of suitable connectors.
Consider water blocking technology under the following conditions:
- Cable will be used outdoors
- Cable will sit in standing water
- Cable will be used in an underwater application
- Cable will be constantly exposed to high-humidity or wet conditions
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QWhat is water blocking in a cable?
It is a construction that stops water from wicking along the inside of a cable. Dry tapes or gel compounds fill the spaces between conductors so a breach at one point does not let moisture travel the full length.
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QIs a jacketed cable already waterproof?
No. A jacket resists water at the surface, but it does not stop moisture from traveling inside the cable once the jacket is cut, cracked, or terminated. Longitudinal water blocking is what prevents that internal travel.
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QWhat is the difference between dry and gel water blocking?
Dry water blocking uses swellable tapes or yarns that expand when they contact moisture. Gel water blocking fills the interior with a compound. Dry is cleaner to terminate; gel gives maximum exclusion for continuous submersion.
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QWhen do I need a water-blocked cable?
Consider it for outdoor runs, standing water, direct burial, underwater use, and high-humidity environments, anywhere a cable can be exposed to moisture over its service life. Speak with an engineer to match the method to your conditions.