Toilet flush valve sealing

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Old 04-03-16, 10:24 AM
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Toilet flush valve sealing

I'm having trouble with a leaking flush valve and realized I don't understand how the seals are supposed to work. There's a big rubber washer inside the tank where the flush valve mounts to the tank. Then there's the big soft gasket that goes between the tank and the bowl. What is the purpose of each?

In particular, I'm wondering whether the tank should hold water when not attached to the bowl at all? Mine fails this test badly. My expectation was that it should hold water and that the big gasket only matters during flushing. But I'd like to confirm this. Thanks.
 
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Old 04-03-16, 10:38 AM
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Use this as a guide.

 
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Old 04-03-16, 11:07 AM
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Thanks for the reply, but I still don't know whether the tank ought to hold water when not attached to the bowl...
 
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Old 04-03-16, 11:21 AM
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When you say you have a leaking flush valve, is water leaking from the tank into the bowl, or is water leaking down to the floor?

The flush valve has a beveled washer inside the tank and a large nut below the tank. The large nut below has no washer, but it does insert into a "sponge" washer which seals the tank to bowl connection.

I would guess you have the wrong size sponge washer. For example American Standard has several shapes and thickness. If you are new at this, and didn't have a hard time compressing the tank to bowl sponge washer, you probably have the wrong washer.

** Lifting off the tank and seeing if it can hold water is not a standard or useful test.
 
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Old 04-03-16, 12:29 PM
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Thanks. I went and bought a Gerber gasket that is thicker and so far no leaks. Regarding the "tank off" test, I'm an engineer and it's easier for me if I understand how things are supposed to work. I don't understand the point of the rubber washer inside the tank if water can escape the tank around the flush valve mounting hole anyway. If the Gerber thing solves my problem, I guess it doesn't really matter though.

EDIT: I didn't answer your question: water was leaking "out", like it would go onto the floor eventually.
 
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Old 04-03-16, 02:45 PM
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if water can escape the tank around the flush valve mounting hole anyway
The test isn't useless as I said, just not a typical test.
You are correct that if the tank was suspended, water should not flow out of the tank. That's assuming the valve is properly secured to the tank and the flapper is closed.

The tanks job is to drop a large volume of water into the bowl, the sponge washer contains that water and directs it only into the bowl and nowhere else.

Water should not escape around the flush valve at all with a properly secured tank, not even a drop.

If you suspect water is leaking out of the tank, you might have to remove the tank again and replace the flush valve. It might not be tight or the beveled washer inside the tank has failed.
 
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Old 06-30-16, 07:35 PM
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My flush valve is leaking, but onlly up to a poin. When the tank fills up, the water will drain into the bowl slowly for about an inch, and then stops leaking. I replaced the flapper, but it still leaks. I guess I have to replace the entire assembly. I can't figure out why the water only goes down an inch and then stops.
 
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