A lighthouse keeper decides to take a bath an hour before the next lighthouse keeper comes to relieve him of his shift.

This lighthouse keeper is having a bad day. First he accidentally locks himself in the bathroom, so he's not going to be able to get out until the next lighthouse keeper arrives and is able to unlock the bathroom from the outside.

He decides this isn't going to put him off having his bath, and so starts running the bath. Then the bath faucet's knob breaks off! He's unable to turn the bath water off. The walls and door of the bathroom are completely water tight. At this rate, the bathroom is going to be completely full after 55 minutes.

How does our lighthouse keeper avoid drowning?

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    $\begingroup$ This question may be off-topic by our new question criteria. Please let me know if this post makes sense/is helpful, and if you think it applies! $\endgroup$
    – user20
    Jun 10, 2014 at 4:14
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    $\begingroup$ @Emrakul: I find this hard to judge until we see the solution. If there is an answer (that I have not found yet) that makes me say "of course, how didn't I see that" I accept it heartily. $\endgroup$ Jun 10, 2014 at 4:34
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    $\begingroup$ @Ross Well... in addition to the answers below, the door might not be airtight, there might be a way to construct something restricting the water pressure, there might be a way to plug the faucet using a convenient nearby toothbrush or soap, one could argue the room wouldn't completely flood anyway... That's sort of where we're looking with that close reason, to be honest. If one can think of multiple arguable solutions... $\endgroup$
    – user20
    Jun 10, 2014 at 5:05
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    $\begingroup$ This is a bit too close to a situation riddle for comfort, in my opinion. $\endgroup$
    – user88
    Jun 10, 2014 at 20:34
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    $\begingroup$ @RossMillikan - I'm wondering now that you can see the answer, would you call this question off topic? $\endgroup$
    – dwjohnston
    Jun 11, 2014 at 22:02

2 Answers 2


The walls and door may be water-tight, but the bathtub is not, there has to be an outflow. So he just has to pull the outflow-plug.

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    $\begingroup$ But question says by current rate, which means : Rate of incoming water - rate of outgoing water. As per simple lines, I consider current rate has deducted that outflow rate already. $\endgroup$
    – PM.
    Jun 10, 2014 at 9:14
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    $\begingroup$ @PM., yes and outflow rate is 0 when the plug is in. And it is in, since he was going to take a bath. $\endgroup$
    – klm123
    Jun 10, 2014 at 10:16
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    $\begingroup$ Reminds me of the joke where a journalist is visiting an insane asylum to write a story and he asks the director how they determine if someone should be institutionalized and he says, "Well, we fill up a bathtub, then we offer a Teaspoon, a teacup and a bucket to the patient and ask him or her to empty the bathtub." The journalist replies, "Oh, I understand. A normal person would use the bucket because it's bigger than the spoon or the teacup." "No," says the Director, "A normal person would pull the plug. Do you want a bed near the window?" $\endgroup$
    – Neil
    Jun 27, 2014 at 12:20

I see 4 options:

  1. If there is some container (bath wash, pan), he upends it and use the air inside once the bath is full.

  2. If "at this rate" means the current speed (litters per second), then he have more time, since when water surface will go up the water pressure will increase and compensate pressure in the bath faucet knob, therefore the speed will decrease with time, which can easily give him additional 5 minutes.

  3. If he has clothes or towel inside he can use it to plug the faucet hole, this will decrease the speed.

  4. If he has phone he can call someone to help.

P.S. If the water pressure is big enough there is no way to escape: he even can be smashed by it ones the bathroom is full.


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