I bought a house that had been sitting for some time. One of the the issues that I've discovered is that the flapper valve leaks. I've come to this conclusion by turning off the water to the tank and combing back later to see that the water level is lower.

I have already replaced the flapper valve itself, and the leak remains.

  • Can you replace the rubber gasket the flapper valve seals against? It could be old and brittle which prevents a good seal when the valve closes down on it.
    – ChrisP
    Dec 28, 2010 at 0:58
  • Unfortunately, not easily (it will likely be easier to replace the tank). The previous owners had installed a low flow retrofit in the tank that while noble in cause makes it very difficult to work in the tank.
    – user1405
    Dec 29, 2010 at 3:02

6 Answers 6


Over time the surface of the plastic part that joins the tank to the bowl can get tiny defects in it that prevent the flapper from making a good seal. As Jeff suggests, you could try cleaning that part, or just replace it.


Sometimes when a flapper gets old and begins to fail (disintegrate) it can leave a piece behind stuck to the outflow pipe that it covers. This piece/remnant then prevents the new flapper from getting a good seal. You might want to clean out the tank and make sure there are no remnants of the old flapper stuck in there.

  • There are no remnants of an old flapper on the valve seat - I have scrubbed the seat with an abrasive cleaning pad.
    – user1405
    Dec 29, 2010 at 3:08

I recently had two toilets begin to leak and had a hard time figuring out exactly where. I hate plumbing but decided to do full replacement of the various parts. I purchased two toilet repair kits for about $18-20 each. Instructions on the package explained what to do. When you are done all parts and gaskets that wear or deteriorate over time are replaced and you essentially have a new toilet. It's fairly easy but it does take some patience and careful work so you don't crack the toilet or tank during disassembly or reassembly. It's also a little messy since you have to get all the water out of the tank. I also replaced the line from the shut-off to the tank so everything is new. It took about an hour for each toilet but now I don't have to deal with something else needing to be replaced next year. Well worth the investment of time and money. And I felt good about doing something successful with plumbing. But I still hate plumbing.


You might consider replacing most of the insides of your toilet. A nice kit is Fluidmaster's S2DBL ($56 on Amazon or about $42 at Home Depot). I used this to replace a low-flow retrofit that a previous owner installed -- the flow was often insufficient.

The S2DBL kit includes a replacement ballcock, flush valve, task gasket, and bolts. Because it's a dual-flush kit you can configure it to use less water, without sacrificing the ability to do a full flush when you need it. If you haven't installed a kit like this before it will probably take 1.5-2 hours, but this kit has good visual instructions and Fluidmaster has excellent phone support if you need it.


Home Depot sells a toilet flapper that comes with a new piece that the flapper rests on. The new piece isn't a replacement, but actually comes with a tube of silicone and seals on top of the old piece. I can't remember the name of the product, but you'll find it with the other toilet flappers for about $3 to $5.

I had this same problem and this particular flapper worked for me.

  • I'd post the link, but I'm having trouble finding what it's called. I think it may have been a Korky product. Jan 5, 2011 at 0:19

I've come to this conclusion by turning off the water to the tank and combing back later to see that the water level is lower.

How much lower? If you turn off the water and it lowers all the way to the flapper valve and no lower, the leak is at the flapper valve and could be the seat if the new flapper doesn't repair it.

If, however the leaking stops above or below the flapper valve, it indicates something other than a flapper valve at the level where the leakage stops.

One common problem on retrofits is if the fill hose from the fill valve is improperly tucked deep into the drain tube, and the water siphons up out of the fill valve and down the drain tube. In this case, when the water supply cut-off is on, you have frequent "ghost flushes", and when the cut-off is closed, the water level will drop only far enough down the tube to break the suction in the fill hose siphon.

When doing a repair, always make sure that the fill hose ends above the filled water level so this siphon problem is impossible.

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