Several Toto toilets have a traditional design and flushing system, which uses a fill valve to let tank water in and a flush valve to send water to the bowl. Fixing common problems that occur in these gravity-fed toilets is a matter of troubleshooting to identify the cause and following guidelines supplied by the manufacturer to make the repair.
If the Toto toilet turns on and off, you will hear the fill valve inside the tank switching on and off repeatedly. The noise is water being allowed into the tank to maintain the tank's water level. The water that the fill valve is replacing is water that the flush valve is allowing to escape from the tank. The flush valve seal gasket needs to be removed and cleaned. Clean it by rinsing it off with running water.
Toilet Won't Stop Running
If the toilet runs continuously, the problem is with the fill valve. When this happens, the tank's high water level will overflow down the overflow tube. The correct water level should be about 1 inch below the top of the overflow tube. On some Toto fill valves, such as on some Promenade models, you can correct this by turning the valve's adjustment screw counterclockwise to decrease the water level. On other toilets, like the Aquia, pull the valve up and set it to the desired level. The fill valve and flush valve seals may be dirty and need to be rinsed off. Shut off the water supply before rinsing the valves.
If your Toto toilet flushes poorly, it may require more than one flush to completely remove the bowl's contents. In this case, you are wasting water. If the toilet's trapway is not clogged, the water level in the tank may not be sufficient to produce a full flush. Again, adjust the tank's fill valve to set the water level at the right point. There may also be a blockage in the vent pipes, which may involve using an auger or garden hose to clear out, but not through the toilet.
If the toilet is slow to refill, you will notice the fill valve steadily running after a flush. Instead of the water level being too high, the water is slower in filling the tank. If the flush valve is properly sealed, the problem is with the fill valve. Similar to the repair for a fill valve that is constantly running and overfilling the tank, the fix for a slow refill is to rinse debris out of the fill valve. Turn off the shut-off valve before removing the fill valve cap. Also, make certain the shut-off valve is sufficiently open so that the water pressure is high enough to fill the tank faster.