How To Adjust a Toilet's Tank Float
Inside the toilet tank is a water valve that controls the inflow of water the refill cycle which begins after you flush. When the toilet is flushed, the water is released from the tank and the float which sits on top of the reservoir of water in the upper tank, drops down, engaging the tank water valve to release water into the tank.
The tank float triggers the tank valve when to start or stop filling the tank with water. If the toilet's tank float is misadjusted the toilet may never stop filling, it may under-fill resulting in insufficient water to properly flush the bowl, or you may be simply wasting water by filling the tank with more water than is needed to flush the bowl.
To adjust the tank float, you simply change the height at which it causes the water valve to shut off. By increasing the height of the float, more water will fill the tank. Lowering the float reduces the water level.
Start by remove the tank lid from the tank and set it carefully onto a towel. Vitreous china can easily scratch other surfaces, so a towel is recommended to avoid damaging the lid itself or any surfaces in your bathroom.
If the toilet fills continuously
Look for the overflow tube. If the water level is at the top of the overflow tube, then you should adjust the tank float lower to reduce the water level. If the float is properly adjusted and the valve still is on, the problem may be with the tank valve.
If the toilet does not flush the bowl completely
You may need to increase the amount of water used per flush. This can be adjusted by raising the tank float.
If you want to conserve water
To conserve water, you can reduce the amount of water used per flush by adjusting the tank float down. Reduce it as far as you can while still achieving satisfactory results in clearing the bowl.
How to adjust the tank float
There are several styles of floats. In older toilets, the float hangs at the end of an armature, along metal or plastic rod. Where that arm connects to the water valve there is usually a screw. Adjusting that screw will change the level at which the water valve shuts off. If there is no screw or it is already at its maximum, you may be able to bend the metal arm, but you should remove it from the valve or risk damaging the fill valve.
In newer toilets the float is often a collar around the fill valve and rides up and down vertically. The float typically has a spring clip connecting it to a metal rod which connects to the valve shut off control. Squeeze the spring clip to slide the float up or down the metal rod.
Manufacturers have several variations on the fill valve mechanism, but they all include a method for adjusting the water level. Close inspection should make it clear how to adjust your particular fill valve.