How to Troubleshoot Low-Flow Toilet Flushing

Low-flow toilets were introduced in 1994 and are are now required by federal law in all new toilet installations. A typical low-flow toilet uses a little over 1 1/2 gallons per flush, which is less than half of the water the toilets that preceded it used. Since introducing low-flow toilets, manufacturers have made many design modifications to make them increasingly efficient. You may still have flushing problems, however, and if so, the cause may be insufficient water in the tank, too much slack in the flapper chain, a partial clog, blocked vents or a combination of these conditions.


Flush your toilet and look at the date stamp on the inside of the tank before it refills. If the date is from 1994 to 1997, home improvement expert Tim Carter advises that it will always take two flushes to empty the bowl. He recommends replacing early versions of low-flush toilets with contemporary ones.


Open the tank and check the tension on the flapper chain. If it is too loose, the flapper won't open all the way when you flush and the tank won't empty completely. Tighten the chain until you can't pull it more than one inch without raising the flapper.


Check the tank level when the fill valve shuts off if you are getting incomplete flushes. It should be about one inch below the opening of the overflow tube. Raise the level by adjusting the float. Adjust a ball float by screwing the ball clockwise to shorten the armature. Alternatively, if the armature has a bend, turn it so the bend is facing into the tank. If the toilet has a cup-style float, unclip the adjustment rod, push the rod and float upward to shorten it and reattach the rod.


Plunge the toilet to remove partial blockages that are creating slow draining after a flush. Ensure the bowl is full when you plunge so that the plunger is directing water -- not air -- at the obstruction.


Clear a blockage that you can't remove with a plunger, using a toilet auger. Feed the auger into the bowl and crank the handle while you push it through the pipes. When the going gets tough, pull it out and clear the head.


Check the vent opening on the roof if the flushing is sluggish but you can't find a blockage. The vent opening may be blocked by leaves or other debris, preventing air from entering the waste line. Clear any debris from the opening.


Feed a garden hose into the vent opening and turn on the water to clear debris that has collected in bends in the pipes. If that doesn't work, feed a sewer auger into the vent opening and crank it through the obstruction.