The water level in a toilet bowl is a direct reflection of the level in the tank. The toilet tank contains the flush and fill devices; the latter controls water levels and usage rates. A water level that is too low will cause incomplete flushes, necessitating multiple attempts in order to clear the bowl. A water level that is too high will cause the toilet to "run" continuously or intermittently.
Don't Flip Your Lid
Remove the toilet tank lid to access the fill valve, but only after reading the following precautions. Before you remove the lid, have a storage site in mind that will accommodate the lid's lying flat and level. Never lean it against anything or allow anyone to stand on it or strike it in any way. The heavy, slippery lid is constructed of a china-like material and cracks easily. Make sure the lid and your hands are dry for safe handling. A broken toe is no fun, and neither is shopping in salvage yards for a colour-matching replacement lid that fits properly.
Valve Style One
There are three types of fill valves for residential commodes.The oldest and most common uses a "float" on the end of an arm. To adjust the level for this style, simply twist the ball up or down the threaded arm to raise or lower the level. If the float is adjusted to the end of the threads and still does not provide the adjustment required, bend the arm slightly. Use both hands for this and make the bend between your hands; this method will prevent damage to the valve. Bend the float end of the arm up to raise the water level and down to lower it. Never adjust the float ball to a height that puts it in contact with the lid when reinstalled.
Valve Styles Two and Three
Another popular valve style is a one-piece construction in which the float slides up and down the shaft of the valve. These valves have an adjustment rod that resembles a long plastic screw that passes though the valve arm and threads into a receiver on the float itself. Twisting the screw raises or lowers the float and, ultimately, the water level. A third design has fallen out of favour, but you may still find it in some residential applications. White in colour and much smaller in comparison to the other styles of valves, these also have an adjustment screw, but no float or visible moving parts.
Flush With Victory
Set the water level in the tank one 1/2 to 1 inch below the top of the overflow pipe. This overflow pipe is in the centre of the tank and looks like an empty pipe standing on end. You may need to make periodic adjustments as the valve ages and some parts wear. Water pressure and purity are also factors that determine how often an adjustment is needed. Consult a licensed and certified plumber if you don't get the desired result or if you have a tankless toilet. Most tankless commodes are installed in commercial buildings and are too complex for the average do-it-yourself repair. It may not seem like a big deal, but ineffective operation of the commode can turn into a dramatic event, to say the least.