Just how dangerous is the interaction between leaking water and my ceiling light?

March 20, 2010 8:18 PM

Water leaking from an upstairs apartment seems to be short-circuiting a ceiling light. How dangerous and how urgent is this problem?

Water has been leaking into my bathroom for ~10 days now. It is coming through the ceiling-mounted switch that controls the bathroom light (also on the ceiling) and the fan. There is a picture of the leak here, if that helps.

Today I noticed that the bathroom light, which is switched off, is flickering and at least a little bit light most of the time. As a non-technical person, I'm guessing that water is completing a circuit somewhere to turn the light (somewhat) on.

The leak is apparently coming from two floors up. Both the flat immediately above mine and the one above that are council flats, so getting the leak fixed is a bit of a bureaucratic nightmare. I own my flat and have insurance, but that doesn't help much since the site of the leak is not in my flat. I have made a number of calls about the leak in the past 10 days, but there is nobody to call now until Monday, unless I call the emergency line, and even then I'm not sure what, if anything, they will do.

So:

1. How dangerous is the situation if I leave things be (and continue not to use the light switch) until Monday morning?

2. Is this a fire hazard? (Can a short-circuit by water cause a fire?)

3. Do I need to try to turn off the relevant fuse, at least while I'm out or sleeping? I think that the bathroom is on the same fuse as my home office, so I won't be able to work properly when the fuse is off.

4. Does this warrant a call to the emergency line? Is there anything that I could have fixed from my end while the leak persists?

Thanks in advance for the help. I am exhausted right now but a bit anxious about going to bed with the problem unresolved.

posted by sueinnyc to home & garden (13 answers total)

As long as the light fitting itself is dry, removing the bulb from its socket will break the circuit and minimize the likelihood of Bad Things happening inside the switch.

After the leak is fixed, the switch will probably want replacing.
posted by flabdablet at 8:51 PM on March 20, 2010

Also: lighting and power are generally not run on the same circuit, so even if the bathroom and home office lights are on the same fuse, that shouldn't cut power to your office equipment. Could you get by temporarily with a bright floor-standing lamp directed at your office ceiling?
posted by flabdablet at 8:56 PM on March 20, 2010

flabdablet, the water is completing the circuit as well. Removing the light bulb possibly reduces the fire hazard, but it doesn't reduce the electrocution hazard. I'd be a little nervous around this situation.

Is it possible to shut off the power to that light with a circuit breaker or other switch that's (electrically) upstream of the flooded switch box? That'd be the safest thing to do while waiting for a repair.
posted by hattifattener at 8:58 PM on March 20, 2010

Whups, I managed to forget that you'd written (3) while writing my reply.

I think turning off the fuse while you sleep or are away would be an excellent idea. Turning it on again during the day so you can work is … I don't want to say "safe" but I'd probably do it if I were in that situation.
posted by hattifattener at 9:00 PM on March 20, 2010

One more thing: The wet cord hanging from that switch could be, to some extent, live. Probably not a good idea to touch the cord barehanded while standing barefoot on a damp bathroom floor. If children or visitors are a factor, you might want to pop on a pair of rubber gloves, stand on a wooden chair, and tie it up out of reach.
posted by flabdablet at 9:00 PM on March 20, 2010

Thank you, flabdablet! I like your thinking about the office equipment If that's the case here, I probably can manage, more or less, without the home office light. I get a fair amount of natural light by day, and can move a lamp in the evening if need be.

Additional advice still welcome:-)
posted by sueinnyc at 9:01 PM on March 20, 2010

The rubber gloves and chair are to guard against the possibility that you pulled the wrong fuse before starting, by the way, not to act as a substitute for doing so.
posted by flabdablet at 9:02 PM on March 20, 2010 [1 favorite]

And thank you, hattifattener!
posted by sueinnyc at 9:02 PM on March 20, 2010

This would be a fire hazard if you kept using it - flipping the switch or left it on, but not if you just leave that fixture off. If your sure that no one will hit the switch accidentally (no kids or sleep walkers around?) then you don't really need to turn off the rest of the circuit. (If it wasn't going to effect a lot of equipment of necessary rooms though, killing the circuit wouldn't be a bad idea.)

This isn't an emergency, the light part is less than the water part really, but if you called the landlords during daylight even on a weekend on this, they would have a lot of room to complain. And that water can make the whole ceiling fall!
posted by Some1 at 9:06 PM on March 20, 2010

If you call the emergency line, they should have a handyman that can come-in and disconnect the switch for now, it's probably shorting/arcing in there as you suspect due to the leak. They don't want a fire any more than you do. Failing that do you have any friends or family nearby that are handy? It's really just a simple switch. Remove the two screws to expose the wiring and disconnect them, with the power off of course.
posted by hungrysquirrels at 9:13 PM on March 20, 2010

the water is completing the circuit as well.

Maybe, maybe not.

Ceiling light switches generally have three terminals: supply, lamp, and loop. For a circuit to exist that doesn't go through the light socket, there would need to be water bridging the loop terminal with at least one of the other two.

The spacing between the internal switch contacts, even when the switch is off, is likely to be rather smaller than the spacing between its terminals. The switch body is also likely to be better at retaining water than the fitting it's mounted in, which has a nice drain hole in the bottom where the cord comes out.

So the most likely pair of contacts for water to be bridging is the ones inside the switch, and those are electrically in series with the lamp socket. If no current can flow through the lamp socket because the bulb is out, no current can flow through the switch contacts either.

Even so, pulling the appropriate fuse as well is a good idea.
posted by flabdablet at 9:18 PM on March 20, 2010

I managed through trial-and-error to flip the fuse, and will call the emergency line tomorrow. I'm delighted to report that the office equipment does still work although the office light doesn't.

Thank you all.
posted by sueinnyc at 9:25 PM on March 20, 2010

This would be a fire hazard if you kept using it - flipping the switch or left it on, but not if you just leave that fixture off.

There are live and neutral wires in that switch always unless the fuse is pulled.
posted by malp at 9:42 PM on March 20, 2010