I have a Toto toilet G-Max Model CST784SF. My problem is that the toilet does not flush properly, not all the time, but often enough so that I have flush a second time. It is as if there is not enough water going down or that the flapper valve is closing too quickly. Also the level of the water in the bowl after flushing seemed a little low. The toilet is not clogged or restricted. I have enough water pressure. The orifices around the bowl are clean and clear. However, a while back I replaced the flush valve with a Fluidmaster A400 instead of the original Toto flush valve. Would that have made the difference? Perhaps the refill tube is not supplying water into the overflow pipe to raise the water in the bowl after flushing.

Is the water level a half an inch below the white overflow tube? Is the little tube from the flush valve inserted into the white overflow tube? How far down in the tube is it? Describe the flush. Does the water come up to the top of the bowl and just swirl around? Let me know, Tom

Yes, the water level is one inch below the rim of the white overflow tube.

The little tube from the flush valve is not inserted but clipped around the rim of the white overflow tube. All water coming out of the refill tube goes into the overflow tube.

I believe I mentioned that this toilet is the 1.6 gpf type Toto G-max type as opposed to the standard 6 gpf type.

When I actuate the flush handle and release it immediately I observed the flush valve opening but shutting down right after I release the flush handle. The flush valve does not have a delay mechanism but rather has a side hole allowing the air to release as the valve closes. TotoUSA said this is by design. I observe water going freely into the toilet bowl from around discharged holes around the bowl. The water does not swirl. Most times the waste go down the drain but sometimes not all so that I have to do a second flush. After flushing however it seems like there is not enough residual water in the bowl, as if not enough water is going into the overflow pipe. I experimented by adding more water into the overflow pipe after flushing to increase the amount of water in the bowl. Then flushing it and that seem to work. So I was wondering if the Fluidmaster fill valve allows adequate water to fill the tank properly but not enough to add enough water to fill the bowl properly. Does the level of residual water in the bowl after flushing affect the way the toilet works?