The fill valve is arguably the most important part of the standard gravity flush toilet. This is the component that controls the water filling the holding tank, the part that opens the water flow as the flush cycle empties the tank, and shuts of the water supply once the tank has refilled to the proper level.
Next to leaking, problems with the fill valve (also known as the ballcock) are the most common issue with toilets. There are several different types of fill valves commonly found in toilets, and you will need to be able to identify your type in order to make adjustments or replacements to yours. Some types of fill valves use older technologies and are best replaced with a newer type when repairs are called for. Other types of fill valves work quite well and can be replaced with exact duplicates.
It is worth noting is that the plumbing code now requires anti-siphoning capabilities on toilet fill valves. Anti-siphon devices are designed to prevent low water pressure in the water supply lines from sucking contaminated water back into the potable fresh water supply. Such low water pressure can occur during unusual events, such as a break in a water main, or when copious amounts of water are being used to fight a major fire, for example. For toilet fill valves, the anti-siphon device is a vacuum breaker or an air gap, and it is located on the side of the valve where water flows through the refill hose and into the overflow pipe.
The five most common fill valves you may find in your home include:
- Plunger/ Piston Type Fill Valve
- Diaphragm Type Fill Valve (brass body)
- Diaphragm Type Fill Valve (plastic body)
- Float Cup Type Fill Valve
- Float-less Type Fill Valve
Here's more information about each of the five fill valves.
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Plunger / Piston Ballcock
Plunger or piston style fill valves (ballcocks) are among the earliest style of toilet tank fill valve designs. They are made of a heavy duty cast brass body that provides quiet operation. This style of ballcock uses a characteristic bottom-fill water discharge tube and is designed with a hinged lever assembly above the ballcock, which often use thumbscrews at some hinged joints to allow adjustment of the lever arm movement. These fill valves work by means of a floating ball attached to a pivoting lever that opens and closes a plunger stem fitted against a water inlet port—hence the name ballcock.
The de facto standard in early plunger style fill valve was the Mansfield 09, many of which are still in service today. In 2007, Mansfield’s brass division was purchased by Prier, an excellent-quality brass plumbing and industrial products manufacturer. The Mansfield 09 is still manufactured by Prier but the ballcock is not listed as anti-siphon by the manufacturer. Wolverine Brass makes a similarly styled anti-siphon ballcock called the Wolverine Model 50568 (10”) or the Model 50569 (12”) They also make an adjustable height anti-siphon plunger ballcock, Model 56568. Cesco Brass also makes a similar style anti-siphon plunger ballcock called the Burlington 20A.
If you have one of these old-style fill valves they should be replaced because they do not meet current plumbing codes calling for anti-siphon protection.
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Diaphragm-Type Ballcock (Brass Body)
Like the plunger or piston ballcock, diaphragm ballcocks have been around a long time. They have strong similarities to brass plunger-type ball-cocks (they also feature a float ball) but they have some important differences.
One such difference is that these ballcocks are anti-siphon. They can come in a cast brass body or plastic body construction. Rather than a plunger stem with a washer that seals against the water inlet port, this type of ballcock has a diaphragm seal that opens and closes to control water flow.
Cast brass construction is found on older models, such as the Mansfield 07 or the Wolverine Model 58577, both of which are anti-siphon. On an older style diaphragm ballcock, the bonnet or cap is made of cast brass just like the rest of the fill valve body. The button that actuates the diaphragm is plastic, however.
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Diaphragm-Type Ballcock (Plastic Body)
Plastic body construction is what you find on most newer model anti-siphon diaphragm ballcocks, and is probably what you will buy if you are choosing to replace a ballcock type valve with another ballcock. Note that this all-plastic type still qualifies as a true ballcock, since its operating mechanism makes use of a float ball.
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Float-Cup Fill Valve
The float-cup fill valve is made of plastic and is a more “modern” style of anti-siphon fill valve, originally introduced in the late 1950’s by Fluidmaster®.
This type is identified by a plastic floating O-shaped cup that moves up and down around the fill valve shaft. The floating cup is attached using a metal spring clipped to a metal actuating rod. Water level in the tank is controlled by adjusting where the actuating rod connects to the float cup.
This is a very popular and easy to maintain fill-valve style. This design accounts for the vast majority of toilet fill valves sold, and it is often the replacement of choice when it comes time to replace an older plunger- or diaphragm-style ballcock unit. Many styles have adjustable shafts, allowing the fill valve to be adjusted up or down to fit different toilet tank depths.
At this stage in the evolution of toilet fill valves, the device no longer qualifies as a true ballcock, since the floating ball has now been replaced by a different mechanism. To this day, though, toilet fill valves of all types are often referred to as ballcocks.Continue to 5 of 5 below.
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Floatless Type Fill Valve
The floatless fill valve is made of plastic and is a newer innovation in anti-siphon fill valves. These fill valves use a diaphragm pressure-sensing mechanism rather than any kind of float device to control the inlet valve. 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. Many professional plumbers avoid them in favor of float-cup fill valves.
You will find these valves attached to the bottom of the tank, since they operate underwater.