Toto toilets have been on the market since 1985, redefining the domestic gravity flush toilet design with new systems regularly. In that time the working mechanisms have seen their fair share of debris and may have developed a slow fill or running toilet issue. Though the mechanisms are proprietary in construction and different in appearance, they are maintainable by the average homeowner. The most common problems are repairable through simple servicing techniques in a few minutes with only basic hand tools.
Pour a small amount of food coloring into the tank and leave the toilet idle for approximately 15 minutes. If dye appears in the bowl adjust the flapper for a tight seal and retest. If the problem persists but the flapper is tight, replace or readjust the flush valve before servicing the fill valve to ensure that the fill valve is the correct problem to address for "ghost flushing" or a running fill valve.
Flush the toilet and observe the action of the internal components with the lid off.
Turn off the angle stop that supplies water to the toilet and flush the toilet.
Disconnect and remove the black supply tube feeding the top of the flush valve.
Remove the cover to the fill valve and inspect for debris. Remove visible debris.
Remove the internal float by carefully depressing the float arms inward.
Hold the fill valve body with one hand and twist the cap (usually black or blue) counterclockwise and remove it. Be careful to avoid twisting the fill valve body. Doing so will unlock the fill valve height adjustment.
Clean the cap assembly under warm water, checking the diaphragm for a tight seal and freedom of movement.
Lift out the center tube from the fill valve and remove the strainer.
Check for signs of debris and rinse all parts under warm water.
Replace all parts in reverse order of the steps listed above and test the toilet operation.
Test flush and check for leaks. Repeat Step 1 to verify all components are operating as described in the manufacturer's specifications.