Dual Push Button Toilet Flush only works if tank lid is removed & button is pressed for 5 seconds

15 Feb 2024
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I have a Dual Flush Push Button Toilet flush that is probably 15 years old. No problems at all in the past - one press & the Half Flush and Full Flush release water.

But, about a week ago, the "Half Flush" button stopped releasing water completely &, about the same time, the "Full Flush" button would only work if I kept the metal button pressed for at least 5 seconds.

Eventually the external Full Flush button also stopped working. No water would be released no matter how long I kept the external metal button pressed, even though the tank was filled to the normal level, which I checked by removing the lid.

However, after removing the lid, when I pressed the actual "Full Flush" button inside the tank, the flush worked perfectly; except I had to keep the button depressed for about 5 seconds. Initially, the water only trickles out, but as the water level drops in the tank, the normal full flow of water out of the tank resumes.

But, the Half Flush button still does not release any water, when I tried pressing the button inside the tank after removing the lid.
So, for now, I've just removed the lid & using the Full Flush only without any problems - other than it looks ugly to have a toilet without the lid on the tank.

I'm buying a new Flush Valve & new metal buttons, but just wanted to know if anyone has encountered the same issue and how they fixed it.

Thanks for any assistance.
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I did hear of something similar...sort of.....

When a toilet is flushed the water exits the tank quickly and and a large volume of air needs to enter the tank to replace it, otherwise a vacuum is induced. In the instance I refer to, the tank had been surrounded by a sealed enclosure (owner had an insect phobia) which prevented the air getting in fast enough and stopped the water exiting properly.

This is not probably likely to help you as you say the problem only recently occurred, without problems in the past. But has anything been changed or sealed up recently that might have an effect?
Thanks for the reply. Can't think of anything that's changed; other than passage of time! Let's see what happens when I install the replacement Flush Drain Unit. Thankfully, because the flush can work when the tank lid is removed I've not had to urgently get it fixed & will attempt a DIY. Online instructors are a huge help, so thanks for any input.

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