I am fixing a small leak from the tank into the bowl.

I bought the Korky complete toilet repair kit and am following the installation instructions in their 5 minute video (https://www.korky.com/4010MP)

After I removed the toilet tank, I am surprised to see a rubber thingy on the toilet bowl:

rubber thingy

There is just one, on the left side.

The toilet manufacturer's installation instructions don't say anything about a rubber thingy.

And it looks like there ought to be two of them, one on each side? It just seems odd to me that there is just one.

What's going on here? I'm a bit puzzled.

Should I just pretend I didn't see it, replace the tank innards and put the tank back on the bowl like it was, or is this something I should address? (Like put a 2nd rubber thingy in there?)

  • 6
    Other one may have fallen into the hole. Aug 5, 2022 at 12:33
  • 2
    I added an edit to be answer that both pieces on each side should be the same size.
    – crip659
    Aug 5, 2022 at 16:18
  • 1
    /Should I just pretend I didn't see it/ - as though you had caught it in some questionable behavor. that is pretty funny!
    – Willk
    Aug 7, 2022 at 1:25

4 Answers 4


My guess, and I believe we are all just guessing, is that this piece is superfluous and may even be the cause of your leak. Throw it out.

The tank should rest firmly on the donut washer that joins it to the bowl. It's an odd design you have, with raised flanges in the bowl along the front and back of the tank. But the tank should not rest on those. If it does, they will prevent you from sealing to the bowl correctly. The tank should not need protection from the bowl for which it was designed. If the tank needed protection from those flanges, you would need them both in back and in front and it would ruin the whole aesthetic of the toilet. You'd need four of them, or perhaps a pair of long protective strips. Ugly.

I don't know why it's there, maybe it was something to do with shipping when the toilet was new, but my guess it that it should not be there.

  • Since toilets are generally placed against a wall, and people generally only lean against the front of the tank (pushing it back), bumpers only on the back could make sense; with the gasket in place and the tank bolted down, there wouldn't necessarily be a need for front bumpers, and since the rear ones are likely against a wall, there's no aesthetic to ruin. They might also take some stress off the gasket when people do lean against the tank, increasing the gasket's longevity. Of course this presupposes they were a manufacturer addition in the first place.
    – Doktor J
    Aug 8, 2022 at 16:54
  • If people reclining on my toilet were my problem I'd stuff a random piece of rubber between the tank and the wall, rather than find a specially shaped piece that fits the way this one does, and put it where it has the least available leverage.
    – jay613
    Aug 8, 2022 at 17:02
  • But if it's a problem the toilet manufacturer is addressing, their greater concern would be the porcelain-on-porcelain interaction between that flange on the rear of the toilet and the bottom of the tank -- which would make it the ideal place for a pair of specially-shaped bumpers. Not to mention, being wedged between two solid pieces of porcelain reduces (but evidently doesn't eliminate!) the chance of the bumpers coming off, versus something just glued on to the back of the tank.
    – Doktor J
    Aug 8, 2022 at 19:27
  • (note: I'm just hypothesizing about why they might be an intentional, manufacturer-placed component of the toilet; not insisting that they are)
    – Doktor J
    Aug 8, 2022 at 19:29
  • 1
    I threw away the odd part; the tank has been resting on the donut gasket alone and there's been no more leak into the bowl. Aug 27, 2022 at 20:47

Looks like a rubber bumper, to keep the tank from hitting the bowl hard.

I would check the bottom of the tank, the second one might be struck to the tank.

If not found, consider cutting a piece of rubber hose to replace it.

Both sides should be equal in size, so if using a rubber hose or something that is different in size of the black piece, replace both sides.

  • 5
    Yeah, porcelain on porcelain is bad news. Aug 4, 2022 at 16:19
  • 6
    Rubber bangy butty bumpers? Aug 5, 2022 at 15:46
  • 2
    Downvoted because, respectfully, I think it's wrong.
    – jay613
    Aug 5, 2022 at 16:53
  • 3
    While I agree these are bumpers it depends on the toilet. No such bumpers on our toilets but the gasket between toilet and tank precludes any porcelain on porcelain contact once the bolts are tightened down. Aug 6, 2022 at 3:00
  • @LorenPechtel with those flanges, a matched pair might make sense as additional reinforcement for when people lean against the tank while sitting. This also would explain why they're only in the back and not necessary in the front (contrary to jay613's supposition that four would be needed) if they were intentionally placed by the manufacturer.
    – Doktor J
    Aug 8, 2022 at 16:52

That rubber thingy looks like someone's improvisation to stop the tank from rocking. It probably doesn't belong if everything in the kit is doing its job.


The rubber gasket on just the one side was likely put in place to help level the tank and the water level inside the tank. This is often done when the floor the bowl sits on isn't completely level.

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