How to figure out exactly where a bathroom leak is coming from

bathroomleaktroubleshooting

There's a small amount of water at the lowest point on my bathroom floor. It looks clear and doesn't have a smell. Lately, it's been showing up every day, whether anyone's taken a shower or not.

How can I be absolutely sure where this water is coming from?

A few sources come to mind:

  • The base of the toilet.
  • The supply line feeding the toilet.
  • The sink across the room.
  • A leak in the roof somewhere over the bathroom.

Overall, the house is of…unusual quality. No one's exactly sure when it was built. On the one hand, the interior is all fairly new. On the other hand, there are knotholes in the exterior walls that were "repaired" by having a tin can lid tacked on over them.* Bottom line: I'd believe just about anything could be the source of this water.


*Surprisingly, you'd never notice the tin can lids unless you were really paying attention.

Best Answer

I see this problem frequently and almost always find the leak by surrounding the suspected area with paper towel laid flat on the floor and then flushing the toilet 3-4 times or filling the sink and draining it 3-4 times. The paper towel will always visibly moisten when the leak starts.