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Does water damage a fiber optic / cat5 cable [Resolved]

One of the buildings I support recently had an adventure with a broken fire sprinkler. Lots of water everywhere.

One of the "drains" the water used was the vertical risers between network closets. The cable plant in this building has bundles of cat5e as well as conduit with bundles of multimode fiber optic cables. The fiber is standard multi strand plenum rated stuff that terminates in boxes that have the patches to the switches.

As far as I can tell, no water got near the ends of the cables (fiber or copper) but the conduit was saturated, and is likely still saturated because there isn't any air flow to dry the cables out.

My gut reaction is that while it didn't do the cables any favors, it likely also isn't going to cause any problems. A little more reading / googling around leads me to believe that the water may cause problems down the road.

Some pretty pictures so everyone knows what I'm talking about:

Fiber conduit: Fiber conduit

Vertical riser, going down: Vertical riser, going down

Vertical riser, going up: Vertical riser, going up

Does anyone have any experience with this sort of damage and how to deal with it? Should we just ask the insurance adjuster to add "pull new structured cable" to the list of things to be replaced?

And, if the opinion is "replace it because it'll start failing randomly over time" please include links that describe the specific failure modes, so I've got some ammo to use with the adjuster.

Question Credit: chris
Question Reference
Asked September 14, 2019
Tags: fiber
Posted Under: Network
8 Answers

The real danger is at the terminations, where corrosion can start. As for the cables themselves, they're fine in water, although I'd be careful using it in a corrosive solution. Keep an eye open and you should see plenty of examples of network cables, including fibre, used outdoors in the weather. I know of examples where cables sit permanently in water and have done so for many years. Network cabling is no different to any other kind of electric cabling. Keep the ends dry and the rest doesn't matter.

credit: Darwyn
Answered September 14, 2019

Replacing the bundles would be expensive. If you've got it in your budget (or insurance will pay for it), do it.

As long as there were no nicks in the PVC sheathing, you should be alright (

It's hard to tell if you had any nicks in the plastic, but I imagine that you're going to find out. Do you have any spare cables in the bundles? I would save yourself the time of panicking during an emergency and find and label them now. Create documentation on how to replace a poorly performing cable with a spare.

Know that if you don't rerun the cables, this event is going to be the scape-goat for all future network performance issues forever, until more cables are run.

credit: Matt Simmons
Answered September 14, 2019

I don't think the water will have any immediate effect as long as the water never entered the cables--obviously copper wiring will oxidize if given the chance.

My argument for re-running the cable would partly be that you can't reasonably ensure the current cable will dry instead of growing mold/mildew and turning into a slimy nasty mess.

credit: STW
Answered September 14, 2019

Depends on the conditions of the cables, where it got in ect, for example there would need to be openings in the insulation on the cat5 to do any major damage.

Since the passages are poorly ventilated apparently, there also comes into question a health risk with the growth of fungus and moulds.

credit: p858snake
Answered September 14, 2019

Water can affect fiber optic cables and splices if the water freezes, causing a macro-bend, which creates optical power loss.

credit: Dane
Answered September 14, 2019
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