How to Repair a Leaking Toilet

If you discover you have a leak in your toilet, don’t wait to get it checked out. As much as 80,000 gallons of water can be wasted each year by an undetected toilet tank leak. That’s more than 200 gallons of water going down the drain each day. Watch this video to help diagnose why your toilet is leaking … and how to fix it.


  • Pencil or Marker
  • Food Coloring
  • Colored Fabric Softener


  1. How to Repair a Leaking Toilet - Step 1

    Remove lid from tank.

  2. How to Repair a Leaking Toilet - Step 2

    Pour several drops of food coloring or a cap full of blue fabric softener into the tank.

  3. How to Repair a Leaking Toilet - Step 3

    Wait 10 minutes.

  4. How to Repair a Leaking Toilet - Step 4

    Inspect water in bowl to see if there any signs of color from fabric softener or food coloring. If so, the toilet has a leak.

  5. How to Repair a Leaking Toilet - Step 5

    Shut off water to toilet.

  6. How to Repair a Leaking Toilet - Step 6

    Mark water level in tank with marker or a pencil.

  7. How to Repair a Leaking Toilet - Step 7

    Check back after 10 minutes to see if water has fallen below mark. If so, the leak is coming from the flush valve. Watch the video How to Replace a Flush Valve for more information.

  8. How to Repair a Leaking Toilet - Step 8

    If not, check to see if the leak is coming from the fill valve by examining overflow tube to see if water is running into tube. If so, watch video “How to Replace a Toilet Fill Valve for more information.

Read Video Transcript

Did you know that as much as 80,000 gallons of water can be wasted each year by an undetected toilet tank leak? That’s more than 200 gallons of water going down the drain each day. It’s not good for the environment and it’s not good for your wallet, either. The good news is that it’s usually an easy problem to fix yourself.

Today, I’ll give you the project basics that address the most common problems with toilet tank leaks to help you get started before you head to your local independent home improvement retailer. That’s where you’ll find everything you need, including the tools and materials, , and the right know-how, to complete this project on your own.

There are two common problems that generally cause a toilet to leak-either a problem with the flush valve which looks like this) or a problem with the refill valve (which resembles what I’m holding here).

Since minor leaks many times go unnoticed, an easy way to determine if your toilet leaks is to pour some food coloring or blue laundry fabric softener into the toilet tank when it is fully refilled after a flush. Give it a couple minutes and then inspect the toilet bowl for signs of color. If the water in the bowl is blue, you know there’s a leak.

But before we start troubleshooting whether your leak is coming from a flush or a fill valve (or a specific component), if the internal parts of your toilet look like they were made twenty years ago it will save you time and money in the long run if you replace all of the toilet tank components at once. It doesn’t take that much more time, and most toilet repair parts manufacturers make complete replacement kits with everything you need for around $20.

You’re also going to need some tools to complete this project, so be sure to click the Tools and Materials checklist button to for a complete listing of everything you need.

If you discover you have a leak and the parts in your toilet tank look relatively new, then you should first determine if your toilet problem is with the flush valve or the fill valve. This takes a little more investigating, so let’s get started.

The most common cause of a leaking toilet tank is when the flapper fails to seat properly and form a tight seal against the valve seat. This lets water leak from the tank into the bowl. It may be caused by the flapper being out of position. It might also be caused if there is a mineral build-up on the bottom of the flapper that prevents it from “seating” properly. If you see a scaly build-up on the bottom of the flapper, shut off the water and drain the tank by holding down the flush lever until the tank is completely drained. You can remove the scaly buildup with steel wool or fine sandpaper. You can also buy a new replacement flapper for a few dollars.

As the water leaks out of the tank and into the bowl, it is then replenished by the fill valve, causing a continuous flow of wasted water. To check for this, first shut off the water supply to the toilet. Mark the water level in the tank with a pencil or marker, then check it again in 10 or 20 minutes. If the water level has fallen below your mark, the flush valve is leaking. If not, the flush valve did not leak, and you know that any leaks are being caused by the fill valve.

If the fill valve isn’t working properly, the tank will generally overfill through the overflow tube, and the excess water will continue to run into the toilet bowl. This is usually either caused by a waterlogged float or when the water level is set too high. A good rule of thumb is to set the water level about 3/4″ below the top of the overflow tube.

If your fill valve has a threaded shank to adjust the water level, push the lock ring up and turn the shank to adjust the height, which will then adjust the water level.

If you have questions about this or any other home improvement project, be sure to read our list of Frequently Asked Questions for this video. And be sure to print out our Project Instructions, which includes a Tools and Materials checklist, before visiting your local independent home improvement retailer. That’s where you’ll find all the products and helpful advice to complete your project. If you’re not sure where to find your local store, check out our Store Locator.

Good luck with your project and thanks for watching

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79 responses to “How to Repair a Leaking Toilet”

  1. James says:

    Detecting and repairing a water leak is not just hard but merely impossible for a normal human being that do not possess plumbing knowledge. Therefore, I would recommend to avail the services of a plumber or plumbing company as they do not only possess the experience but all the tools along with that they also have knowledge with respect to latest plumbing techniques to do the job accurately and in a short amount of time.

    • Lee says:

      James your comment must mean you are a super human Plumber since we are all just normal human beings with no knowledge of plumbing. Your post is Coming from a plumber drumming up business. To fix a leaking toilet is not rocket science by any means. Maybe if you have leak in your wall I’d call you but not now with your arrogant remark. As for a toilet it’s an easy DIY don’t waste your money on a plumber for this.

      • Jeannae says:

        ,,,,my thoughts exactly Lee

      • Chad Travis says:

        After reading James’ comment I chuckled it off as sarcastic humor. Then after reading your comment I went back to read his again… After deliberation I have a hung jury… He either has air tight sarcastic humor with no leaks whatsoever or he might really be that big of a d bag plumber that really thinks detecting a leaking toilet (which involves hearing your toilet running at odd times) , and thinks changing a rubber flapper is a licensed plumber required, difficult activity.

    • Karen says:

      Wow, for months Iv not been able to get a plumber out in my rented property to fix my leaking toilet i turned the water off about 6months ago, and not been able to use it(good job I have a 2nd toilet) emergency repairs said they couldn’t send anyone out because of the pandemic…
      Well after all this time I happened to log on and watch this Visio, and hay pesto, Iv mended my loo, thank youuuuuuuuuu.
      By the way I’m a 58yrs old woman..

  2. Angus Clark says:

    Thanks for the help worked out great in just a few minutes

  3. Paul says:

    I have an unusual, mind boggling small leak from my tank into the bowl via the flush valve that is driving me nuts. I have replaced the flapper several times with different brands, and even replaced the entire flush valve (Corky product, most expensive I could find) to no avail. I’ve removed the tank and filled the tank off of the toilet and got it so there were no leaks coming from the flapper nor between flush valve and tank but as soon as I attach the tank back on the toilet it begins to leak into the bowl from the tank. There are no cracks in the tank or toilet. Obviously when the tank sits on the toilet, the weight and pressure of the full tank is causing something in the flush valve to become out of round and break a seal some how. I have levelled the tank, tighten tank down snug and then tried backing it off. I’ve tried adjusting the tightness of the two inch nut on the flush valve and yet nothing seems to make a difference. All possible leaking parts and gaskets have been changed. Toilet did not always leak. Stamped date on toilet is 2005. Has anyone run into this unique issue ever or have any suggestions before I replace the whole toilet? Thanks.

    • Karen Roberts says:

      i have this exact problem and cant figure it out, hasnt mysteriously fixed itself for me yet. Could the toilet be leaking at the poo end and the water is constantly running to top bowl up…?

    • L G says:

      I’m in the same boat. Replaced entire flush valve, used three different brand flusher, and replaced the valve seal. I am >this< close to taking the toilet out for target practice. Before I do, my last attempt is going to be drying out the tank completely with a hair-dryer and caulking every surface that may be leaking water. I doubt it will help but man it is so frustrating having this problem in the master bathroom of all places!

      • GP says:

        Make sure the fill tube is cut ABOVE the water level. Otherwise it will siphon the water from the tank and send it into the bowl! I had the same problem, trimming the tube finally fixed the issue!

        • John says:

          I believe this solved my problem. I replaced fill valve and just ran excess fill hose into overflow tube. Had water leaking into bowl. Replaced flapper still leaked. Read this blog ,trimmed fill tube, problem seems to be solved. Thanks

    • Rich says:

      SOLVED….trying to replace Jameco toilet flapper with Fluidmaster flapper…Flapper did not go down all the way so it was leaking. There is a plastic “cross” beneath, preventing it from going all the way down ..
      Flopper “ball” (its part under) was too long. After removing a plastic tip from the rubber “ball”
      (to make it shorter) it is OK now….SOLVED

  4. Paul says:

    Well after tightening the tank down a little more and maybe allowing the flapper valve to climitize to the cold water of the tank, the toilet leak has seemed to slow to almost nothing. Hopefully over time the leak decreases to nothing instead of increasing. Time will tell.

  5. Babs says:

    Anyone help I have a leak in my toilet and it’s not going into the bowl. I have isolated the toilet for now as I’m losing about a litre of water an hour

  6. anupriya agarwal says:

    This is the best website. After watching 5 YouTube videos that did not clearly help me identify the issues, your website helped me identify and fix it in 5 min! Awesome! Congratulations

  7. Antonio Rivera says:

    Thanks for the video. It turns out that my flapper seem to sit well but was oily and did not seal properly. I cleaned the flapper and the rim where it sits and that seemed to do the trick.It was driving my wife crazy when the toilet released a tiny bit of water and made the airy sound, otherwise we did not know there was a slow leak. Your fix worked. Thanks again.

  8. Brian Childress says:

    I have replaced Flaper, flush valve, fill vale and seal under tank. STILL leaks into bowl.O and 3 flappers cause each kit had a new onelast one was with the new fill valve. Ideas??

  9. Roman says:

    I would recommend to call in a professional plumber to fix the leak, because it could lead towards causing some serious damage to your residential property if not fixed properly.

  10. Antonio says:

    Thanks for the invaluable information! Very useful information!

  11. Roy Burbage says:

    I still have a ball system which is the problem. If I could know a way to adjust its level would solve my problem.

  12. mistie says:

    this is sort of an old post but im really stuck with this one…first of all when i flush the toilet it literally pisses out the back of the toilet and its now stsarted to expand the wood in my floor which i suppose i should replace but i cant afford it right now…also i cannot shut the wayter off because the valve is stripped and it keeps turningf and turning and in order to shut the main water off i have to go through my landlord and i dont want her to know because then i wont get my damage de[posit back but im hoping to fix this like it never happened and not worry about losing 700$ damage deposit…so what do i do???

    • John says:

      What kind of a landlady do you have that won’t fix your toilet and will blame you for floor damage that her toilet caused? Get over your fears and tell her she needs to fix the toilet or you’re going to read the fine print of your rental contract and move out or withhold rent.

  13. Sheri says:

    Must be in need of business. Because we have fixed our toilet and 5 months ago fixed our daughters. So please dont try and scare people on here. Dont worry if your a good plumber. You would be doing more important jobs than leaking toilets… so a good job for you that is doing real good every where is pumping skeptics. Seems like you are full of yourself. So you may want to pump your arrogant self first and stop scaring people on here.

  14. Sheri says:

    This comment is to James the super human… hahahaMust be in need of business. Because we have fixed our toilet and 5 months ago fixed our daughters. So please dont try and scare people on here. Dont worry if your a good plumber. You would be doing more important jobs than leaking toilets… so a good job for you that is doing real good every where is pumping skeptics. Seems like you are full of yourself. So you may want to pump your arrogant self first and stop scaring people on here.

  15. Viplav says:

    Thanks for support to repair leaking tank. Nicely explained.

  16. Garry says:

    A simple yet effective method of detecting a silent toilet leak is the pencil test. Start by taking a pencil then take the top cover of the toilet tank off, and mark the waterline on the tank’s interior wall using the pencil, next turn the water supply off and wait for around 20 minutes. Remove the top cover, in case there is a dip in the water level from the marked point then it means that flush valve is leak. This means that you have got a leak on your hands and you need to call a trusted plumber.

  17. VIKRAMAN M says:

    when flushed the closet is leaked from the bottom side to the floor and fsmell bad. what to do is not known. it is fixed in 2016 only

  18. Alex says:

    I have a problem. Periodically – maybe once an hour – I hear that water is pouring into the tank and its level rises a couple of inches. To check where the water goes from the tank, I poured blue washing liquid into it. There is NO leakage in the toilet bowl. There is no water on the floor. BUT some water goes away. Where and how to fix it?

  19. Sara says:

    There are various causes behind toilet leak, it could be due to condensation on the bowl, bathrooms usually get very humid especially during and after a shower which can often cause condensation to drip on your toilet. The leakage could also be due to cracked bow, although toilets are built to last for years, but cracks do sometimes develop on them over time. Often times this will start as a hairline crack that develops into something more severe. Therefore, it is recommended to call in a professional, before the problem further intensifies.

  20. Trevor says:

    Call a professional, call a professional…blah blah blah…it’s pretty basic stuff. If tradies didn’t charge such ridiculous hourly rates we would call them more often , daylight fkn robbery…Why do you think we are reading these types of forums ?.

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