01 of 06
The Function of the Fill Valve
The toilet in your home has several tank components, but there are only two tank valves at work every time you flush the toilet: the flush valve which releases the water stored in the tank down into the toilet bowl when you press the flush lever; and the fill valve (also traditionally known as a ballcock), which controls the water refilling the tank after the flush.
When a toilet doesn't work, it's sometimes tempting to replace the toilet altogether, but in many cases, you only need to upgrade the fill valve to modern standards to return the toilet to perfect working condition.
The Function of the Fill Valve
The fill valve (ballcock) is a device that senses the level of water in the toilet tank—opening to let water into the tank when the water level drops during a flush and shutting off the water flow once the tank is full. If the toilet continues to "run" after the flush, it may well because the fill valve is faulty and needs to be replaced. (The other major cause of this problem is a flush valve that leaks and needs repair.)
When Adjustments Are Needed
Adjustments to the fill valve can be necessary when the toilet fails to flush completely, which usually occurs because there is not enough water in the tank. Each type of fill valve has a method for adjusting the water level in the tank.
The original fill valves used a floating ball mounted on an arm to operate the valve, and for that reason were known as "ballcocks." More modern fill valves no longer use floating balls, but the name has endured, so for many people, the term "ballcock" is generic, referring to any type of toilet fill valve.
Types of Toilet Fill Valves
The fill valve comes in four basic variations, each with a specific method for adjustment:
- Plunger/ piston-type ballcock
- Diaphragm-type ballcock
- Float-cup-type fill valve
- Floatless-type fill valve
Technical tip: Virtually all fill valves have two water outlets. One discharges water directly into the tank, while the other sends a small stream of water down a brass or plastic overflow tube in the center of the tank. This tube is what refills the standing water in the toilet bowl, and is essential for keeping sewer gases from seeping up into your home. Whenever working on a fill valve, make sure this bowl refill tube is directed down into the overflow tube. Note that the tip of this refill tube should be well above the standing water level in the tank. It should not extend down into the overflow tube below the level of the water in the tank.Continue to 2 of 6 below.
02 of 06
Plunger/ Piston Type Ballcock
Plunger-fill valves are actuated by a brass float rod and ball attached to a lever which moves a plunger or piston in the ballcock body up or down to start or stop the flow of water to the tank through the water discharge tube. This is the design that is properly known as a ballcock. The plunger uses an O-ring or leather washer to form a seal to prevent the water from leaking out the top of the fill valve.
How a Plunger/ Piston Ballcock Works
As the water level in the tank rises and falls, the float rod and ball move the lever arm accordingly. When the water level is at the correct height, the plunger is fully seated in the fill valve body and stops the flow of water to the tank. When the toilet is flushed, the water level in the tank drops and the lever assembly moves the plunger up, allowing water to fill the tank again.
Adjusting a Ballcock
There really isn’t any high-tech way to adjust the water level with a plunger ballcock. You simply bend the brass float rod gently upward to increase the water fill level in the tank or gently downward to lower the water fill level. The plunger/piston mechanism should be a minimum of 1 inch above the top of the overflow tube in the tank, and the overflow tube must be below the height of the toilet tank handle that actuates the flush valve releasing the water.Continue to 3 of 6 below.
03 of 06
Diaphragm-Type Ballcock: Brass
This style ballcock is quite similar to the plunger-style, except that the valve itself does not use a plunger stem, but rather a diaphragm seal inside a round valve body. The actuating device used to control water discharge is similar to that in a plunger ballcock since it also uses a float rod and ball (it is therefore often rightly known as a "ballcock," as well). The lever assembly moves a plastic button in the top of the bonnet, which in turn presses against the rubber or plastic diaphragm to control the flow of water.
Tips for Fixing a Brass Diaphragm Ballcock
Older models of the diaphragm fill valve have a bonnet or cap made of cast brass like the rest of the fill valve body, but the button that actuates the diaphragm is made of plastic. Sometimes calcium or other mineral deposits can build up between the brass bonnet and the plastic button, creating friction that causes the button stays depressed in the “closed” position even when the float road and ball have dropped away. When this situation happens, the toilet tank is drained empty and the ballcock does not release fill water to fill it back up.
To fix this problem, spray some penetrating oil into the top of the bonnet where the plastic button protrudes through. Then, work the button up and down by manually moving the float rod up and down so as to depress the button a few times. The button should work free and the ballcock should then operate properly.
Adjusting a Diaphram-Type Ballcock
On older cast brass model diaphragm ballcocks, there is rarely any adjusting screw to control water height. As with the plunger ballcock, you just bend the brass float rod gently upward to increase the water fill level or gently downward to lower the water fill level.
Also, the overflow tube must be below the height of the toilet tank handle that actuates the flush valve releasing the water.Continue to 4 of 6 below.
04 of 06
Diaphragm-Type Ballcock: Plastic
Just like the older brass version of this fill valve, the plastic diaphragm ballcock's actuating device used to control water discharge also uses a float rod and ball. The lever assembly moves a plastic button in the top of the bonnet, which in turn presses against the rubber or plastic diaphragm to control the flow of water.
How to Adjust a Diaphragm-Type Ballcock
On newer plastic model diaphragm ballcocks, there is an adjustment screw on the top that adjusts the height of the float rod and ball. Turning the screw counterclockwise raises the water level while turning the screw clockwise lowers the water level.
Also, the overflow tube must be below the height of the toilet tank handle which actuates the flush valve releasing the water.
Continue to 5 of 6 below.
- Repair tip: The rubber diaphragm in many fill valves of this style can be replaced when they wear out. It is an easy fix that is a lot easier than replacing the valve.
05 of 06
Float-Cup-Type Fill Valve
In this type of fill valve, water flow is controlled by a plastic floating O-shaped cup that moves up and down concentrically about the fill valve shaft.
Although some call this type of fill valve “floatless” because it has no traditional float rod and ball, the description is inaccurate, because this fill valve still relies on the use of a moving float mechanism.
How Float-Cup-Type Fill Valve Works
The floating cup is attached by a metal spring clip to a metal actuating rod that controls the fill valve located under a cover at the top of the valve assembly. When the water level in the tank is empty, the floating cup is at the bottom of its travel, and the fill valve discharges water through a refill hose into the top of the overflow tube. As the water level in the tank rises, the floating cup rises until the water level reaches the proper height and the actuating rod attached to the floating cup closes the fill valve.
How to Adjust a Float-Cup-Type Fill Valve
On traditional float-cup fill valves, the water level is adjusted by moving the plastic floating cup along the metal actuating rod. To adjust the float level, pinch both ends of the metal spring clip and raise or lower the floating cup along the actuating rod, releasing the clip to fix the cup’s location. To lower the water level, adjust the floating cup downward on the actuating rod. To raise the water level, raise the floating cup on the rod.
On some newer float cup valves, there is no adjusting rod at all. Instead, the entire stem of the valve may be adjusted up or down in increments to alter the water level in the tank. The stem is unlocked by twisting the float device, then the stem can be shortened or lengthened as needed, before twisting the float device again to lock it into place.
The water level should be about 1 inch below the top of the overflow tube and the critical level mark on the fill valve. It is important to buy the proper height fill valve, or an adjustable height unit so that the water level can be properly set in relation to the overflow tube and the critical level on the fill valve.Continue to 6 of 6 below.
06 of 06
Floatless-Type Fill Valve
These units use a diaphragm pressure-sensing mechanism rather than any type of float mechanism to adjust the water level in the toilet tank.
Originally designed for low profile/low flow toilet tanks of the 1990s, these fill valves are usually inexpensive, but the design has been known to have a spotty record of reliability. In some locations, in fact, these valves are not allowed by code.
How a Floatless Fill Valve Works
The floatless fill valve is attached to the bottom of the tank and operates under water. When the tank is flushed and the water level in the tank is empty, the floatless fill valve senses the loss of water pressure and the fill valve discharges water into the tank and into the overflow tube to refill standing water in the bowl. As the water level in the tank rises, the floatless valve continues to allow water to discharge until its pressure-sensing mechanism determines the water level has reached the proper height and closes the fill valve.
How to Adjust a Floatless Fill Valve
To adjust the fill valve, you simply turn an adjustment screw located on the top of the valve. To raise the water level, turn the adjustment screw in a clockwise direction. To lower the water level, turn the screw in a counter-clockwise direction.
As with other types of fill valves, make sure the bowl refill hose is discharging water into the overflow tube to ensure the standing water in the toilet bowl gets refilled as the tank refills.
Also, the overflow tube must be below the height of the toilet tank handle that actuates the flush valve to release the water.