The modern low-flow toilet was invented around 1994. It was designed to flush 1 1/2 gallons of water, while still flushing adequately. Previous toilets used up to 4 gallons for a single flush. This simply wasted water. Most low-flow toilets do a terrific job getting rid of waste. There are, however, common maintenance issues that arise. The main problems come from the fill and flush valves. Knowing how to properly fix your low-flow toilet fill and flapper valves is a skill everyone should master.
Things You'll Need
New flapper valve from hardware store
New fill valve from hardware store
Listen for running water or trickling. If you can hear anything, even just slightly, you might have a faulty fill or flapper valve.
Remove the tank lid and peer into the water. The water level should be about 1-inch below the overflow tube. You should see no water movement. Slight ripples indicate a leaky flapper valve.
Shut off the toilet water supply. There should be a valve near the wall. Then flush the toilet to empty the tank.
Reach in the tank and remove the flapper valve (the valve attached to the flushing chain). Examine the underside of the valve for obvious cracks or deficiencies.
Scrape the valve seat with a screwdriver to remove any mineral deposits that prevent a tight valve seal. This could cause leaking.
Purchase and replace with a new flapper valve at any hardware store if this does not solve the problem. The valve could be misshapen from sitting incorrectly for so long.
The sound of continuous water trickling typically means you need to replace the fill valve instead of the flapper valve. New flapper valves only cost about $3.
Some low-flow toilets need to be flushed two times to empty all of it's contents.