How to Adjust a Toilet Ballcock or Fill Valve

toilet ballcock
The toielt ballcock is also called a fill valve. Danco

The toilet is pretty dependable but on occasion it can have problems. You will find that many toilet problems are related to a faulty flush valve (the device that lets water out of the tank) or a faulty fill valve known as a ballcock. Fortunately, you will often find that the ballcock is not defective, just improperly adjusted.

These two tank valves (fill and flush valves) are at work every time the toilet is flushed.

The flush valve releases the water from the tank into the toilet bowl when you press the flush lever. The fill valve (also known as a ballcock) is what controls the water refilling the fill tank after the flush. 

You will find that adjustments to the fill valve become necessary when the toilet fails to flush completely. That often happens when there is not enough water in the tank. Different types of fill valves have their own methods for adjusting the tank's water level. 

The tutorial Adjusting Different Types of Toilet Ballcocks describes the four major types of fill valves available:

  • Plunger / Piston
  • Diaphragm
  • Float Cup
  • Floatless

Also discussed will be why they are different, what they are made from, and how to adjust them for proper operation.