TOTO ST416 quietly hissing

[Apesbrain]

I replaced the fill valve cap as I've done many times before, but I can still hear water quietly running. Might stop for a while after a full flush, but always the noise returns. Have removed/cleaned the fill valve filter, checked the float is not rubbing, brushed clean all contact surfaces. Any other ideas?

One thing I've noticed is that the inner fill tube is very tight and difficult to pull up and out of the valve. I'm thinking of buying a new fill valve and cannibalizing its parts into the old one as replacing the fill valve assembly is a bear on these units; as far as I can tell, it requires the tank to be removed. Can someone confirm? Thanks.

 

[Reach4]

I cannot confirm that replacing your fill valve would require removal of the tank. Seems unlikely, but strange things exist.

1.Regarding the sound, is the fill tube held above the overflow tube, rather than going down the hole?

2. How far below the overflow tube top is the water?

 

[Sponsor]

 

[Apesbrain]

When I look under the rear of the toilet, the connection between the fill line and the bottom of the fill valve is not visible. The metal-covered intake hose disappears up into the bowl unit.

It's a dual-flush unit (see photo) so there is no visible fill tube. Thanks.

 

[Terry]

When I look under the rear of the toilet, the connection between the fill line and the bottom of the fill valve is not visible. The metal-covered intake hose disappears up into the bowl unit.

It's a dual-flush unit (see photo) so there is no visible fill tube. Thanks.

Replacing a fill valve on a TOTO Aquia requires removal and replacement of the tank. It's a good idea to have an extra tank to bowl gasket for those when doing the fill valve replacement.

 

[Breplum]

The hissing is from the little dot gasket which is located under the black float, which comes off by pinching the sides.
My plumbing suppliers often have a bone pile, but in your case, you can buy a Korky or Toto (the same part) and take out the float to use in yours.
I detest Korky/Toto fill valves and prefer simple Fluidmaster, but you may not have room so too much trouble. I never install Aquia anyway, floor mount block is plastic trash as is the slotted tiny hold down screw on each side...