This might sound stupid but I've just changed the diaphragm in the toilet as it was hissing and not filling for a long time.

The toilet flushes great and only takes about 20-30 seconds to fill now, but at the end it makes a quick hiss sound.

I'm assuming this is probably the valve closing fast and that's the sound of the water flowing through but I just wanted to double check that there isn't something else wrong.

Is this normal?

1 Answer 1


Once the tank gets close to full the hiss is the water being restricted until the valve closes and is normal.

  • Thank you, that's what I thought. Is it a problem if I hear the occasional hiss whilst it's filling up? Jan 8, 2018 at 21:53
  • The valve may still be opening If it starts getting slow to fill and you hear the hiss sometimes small rocks block the valve and popping the top and flushing the valve out will usually cure that. There are a few more steps but it should be a while before that is needed.
    – Ed Beal
    Jan 8, 2018 at 22:09

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