Homeowners with older houses often ask how they can stop a constantly running toilet. There are a couple of simple causes with equally simple fixes.
It may be that the flapper isn’t sealing correctly or that the fill valve is improperly adjusted. If the flapper is warped or damaged it’s pretty easy to replace. First, turn off the water supply and empty the tank. Then disconnect the flapper from the flush chain and unsnap it from the flush tower. Snap on a new flapper and re-connect the chain before turning back on the water.
If water is constantly running down the overflow tube, the fill valve needs to be adjusted. Turning the adjustment screw on the valve in one direction raises the water level and the other direction lowers it. The ideal level for a toilet tank is about an inch below the top of the overflow tube.
These simple repairs should stop the constant flow of water through the toilet. But if you really want to save money on your water bill you should probably consider replacing that old toilet with a new one. Some older toilets use as much as 3 and a half gallons of water per flush, while the law requires newer models to operate with a maximum of 1.6 gallons.