I just took apart the valve inside of my toilet to fix a crack in the floater. It's a Fluidmaster 300:

Fluidmaster 300

When I put the thing back together and turn the water back on, no water comes out of the refill tube. Instead, it squirts out of the top of the red cap where the black floater connects.

Underneath that red cap is a rubber diaphram, which i've pulled out and inspected. It's in good shape. it has a little nipple in the middle where a tiny stream of water can come out, and water is coming out of that, but not the refill tube. Anyone know what's going on here?

Edit: I found a little pin in the bottom of the toilet. Is this supposed to go in the nipple of the seal? Looking at the valve, I can't even understand how the arm raising could possibly shut anything off! I feel like I just discovered a glitch in the matrix or something.

  • I'm not familiar with this particular fill valve, but it looks like you may have missed something when reassembling the valve. The pin may be a critical missing piece, or a red herring! One nice thing about some fluidmaster valves is that they're super easy to replace -- you can just move a ring and pop the valve parts off the base tube, and pop on a new one quickly without needing to unscrew the base. Jan 27, 2016 at 21:30
  • 2
    This is a good moment to realize that you when you disassemble something take plenty of pictures so that you can re-assemble it properly.
    – ArchonOSX
    Mar 3, 2016 at 8:39
  • @Archon in general I agree with you, but this was three parts. The issue wasn’t remembering. The pin ejected itself so I never saw it. May 28, 2021 at 12:51

3 Answers 3


The pin should be your problem. You're right, it does go behind the diaphragm, See this video at 58-seconds & 1:30 for an example, & inside the center of the cap.


Save yourself a headache and just remove this damaged unit and fit a Fluidmaster 400A. -Less than $15 and 30 minute's work.


I guess you have resolved this YEARS ago, but since I spend hours even trying to find this part (fluidmaster does not show the part on their page).

Yes, there are a locking piece you are missing there, attaching image of mine ... unfortunately I was trying to adjust mine, and after 'releasing' the lock, I cannot figure out how to lock it again ...

I take this will mainly be useful for other people in the future with the same issue. The piece is going under the pin, and somehow will lock it in place (I might end up trying to figure out on a second toilet), but first see if I can find instruction for how this clip is supposed to work.

The part is the small horizontal part under the long vertical piece.

Close up of floater

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