The thing is, I had a plumber come over and look at the toilet in my house, and found he said it was leaking. However, I do not know how he knew it was leaking.

My question is, how do they tell if the toilets are leaking? I did not see them because my family left the house for the day when he fixed it.

Things I have already tried:

  • Checking around for leaks.

The plumber said to do this before he came, but I found nothing.

  • Hello! Have you thought maybe he lied to you? And had you checked under the house? Also, did you ask him. Maybe he thought that the toilet was leaking internally. I think you should define the question better, because as it is you may not get quality answers. These are just some suggestions. Thank You for your contribution and I hope to see you around Stack Exchange!
    – Pobrecita
    Jan 10, 2015 at 0:26
  • @darthnesscoveredthesky did you seriously JUST change your user picture? Also have fun at 3000 rep Jan 10, 2015 at 0:28
  • If the flapper is failing, it is likely that other parts could be on their way out as well. It is more cost effective to buy an entire rebuild kit which includes the flapper, fill valve and seal between the tank and the bowl. Then you will basically have a new toilet. Replacing the parts is a DIY project. If you aren't comfortable doing it yourself, then a plumber should be able to do it all in about an hour. Jan 12, 2015 at 20:07

4 Answers 4


The plumber may mean the toilet tank is leaking into the bowl through the flapper valve found at the bottom of most toilet tanks, at least in the USA. This is the most common toilet leak.

To test, you can place just enough colored drink powder, KoolAid mix,(preferably without sugar so as not to attract insects) in the toilet tank, do not flush, but wait 5 min. If the water in the bowl begins to change color, then the flapper valve is leaking. This is a wasteful and possibly costly loss of water over time.

Flapper valves cost from $5.00 to $10.00 and are very easy to replace. Buy a good one. Many are guaranteed to last five years. It takes less than five minutes to change the flapper valve. All household toilet flapper valves should be replaced about once every five years. Even a small leak can allow an amazing and expensive loss of water. Areas with hard water cause mineral buildup on the flapper valves, or the rubber becomes hard and the valves do not seat well over time.

If the leak is in the coupling or feed line to the toilet, or if in the water control mechanism, then it may still be a "do it yourself" job, but a bit more tricky, and wet.

If the toilet is leaking around the seal to the floor, then depending upon the age of the structure and installation, it may be a much more complicated job. Again, simplest resolution may be "do it yourself", more complicated could get into heavy plumbing and even carpentry or flooring work.

The next best question from you to the plumber is what part is leaking, and from where to where. Discuss that answer here or with your local hardware or plumbing merchant. Or come back here. Most all of us are familiar with toilets in one way or another. :)

There is no intent to undermine the fine and high degree of integrity in the plumbing profession, but two opinions are almost always better than one.


As lifehacker mentions, you can check if your toilet tank is leaking in this way (essential info):

  1. Put some dye, e.g. green one (anything coloring) in the toilet tank

  2. Don't flush, wait for some time.

  3. If in the toilet bowl you see colored water, your toilet is leaking, otherwise it doesn't.

That's if the leak is small. If it is big, you can detect it just with your eyes :D

There is another way:

  1. Mark the level of water in the toilet tank with chalk (slightly above the water level, otherwise water will remove this mark immediately).

  2. Wait for some time...

  3. Check how the water level in the tank changed comparing to your mark.

I suggested marking the water level with chalk, so as you can remove this mark later with water.

  • 1+ This seems like a awesome method. Could you add some pics perhaps to show us what it is suppose to look like. And couldn't rust water look like the dye? These are just some suggestions. Thank You for your contributions and I hope to see you around! :)
    – Pobrecita
    Jan 11, 2015 at 0:03
  • @dar made an edit.
    – nicael
    Jan 11, 2015 at 7:22
  • I saw. Great job! Only I already upvoted :) Hopefully now this answer will get the votes it deserves.
    – Pobrecita
    Jan 11, 2015 at 7:23

I think the other answers are correct in assuming "leaking" means continual filling of the bowl from the cistern.

But in case they're wrong, way I tend to determine if a toilet is leaking from a seal or other joint is to wrap suspect areas in toilet paper. Sometimes sticky tape is needed to hold the paper in place. Then I check on a regular basis to see if any of the paper has become wet. Even if the paper has since dried, it changes consistency after being wet the first time.

This is normally enough to narrow down to a particular part of the toilet. It can be helpful as well in distinguishing between condensation-based "leaking" and actual leaking from a joint. Condensation or "sweating" on the outside of your cistern is another indicator that your toilet is continually filling the bowl - the water never has a chance to reach room temperature because it keeps getting refilled when the level in the cistern drops.

  • I do the same but add color chalk to the paper, that gives a better impression if they have been wetted and how much. Jan 13, 2015 at 11:09

Remove or displace some water in the trap. Come back in a while and see if the trap has filled up to the usual level. If you have a plunger handy using it will usually leave the water lever below the usual level. If the water is clean using a mop to soak up some of the water is also an option.

  • 2
    Welcome to Life Hacks Stack Exchange and Thank You for your response! My question is how would you tell if the water didn't just precipitate and not leak? And could the not filling be a sign of a different problem and not leaking? Either way this post is off to a good start and just needs some more explanation. For help constructing a post, see the Help Center. I hope that helped, and I would enjoy seeing you around Life Hacks Stack Exchange in the future.
    – Pobrecita
    Jan 11, 2015 at 0:06

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