Common Toilet Fill Valve Problems + Quick Fixes

The fill valve of your toilet combines with the flush valve to ensure your toilet always has enough water to flush and keep everything clean. The fill valve setup is a pretty simple one even when there are various types with different approaches on how to keep the toilet tank full.

No matter what type of fill valve you have, it may develop issues along the way due to a malfunction, age or other cause. Solving these issues requires understanding what kind of toilet fill valve you have as each one has its own procedure for solutions.

If the solutions we offer in this guide don’t work, it’s better calling in an expert or the company that sold or installed the toilet unit for you. For most of these problems, however, the solutions are simple DIY procedures as you will learn shortly.

Toilet fill valve picture
Fill valve

Too much or too little Water in the Toilet Tank

If your toilet tank holds too little water (not enough to clear wastes in one flush) or too much that it overflows, the cause is that the fill valve has been poorly adjusted and needs readjusting. The type of toilet fill valve determines the solution to this issue.


You solve the issue by adjusting the fill valve such that it either allows in more or less water into the toilet tank. The most common types of fill valves and how to adjust each one are as follows:

Piston/Plunger fill valve

For this type of fill valve, you bend the brass rod connected to the floating ball either up to raise the water level or downwards to lower the level. It’s a gentle bend as a small degree of the bend has a major difference on the level of water in the cistern.

Diaphragm fill valve (brass)

This type of fill valve is similar to the piston type save for having a diaphragm instead of a piston. You can also adjusting the water level by bending the brass rod upwards to raise the water level and downwards to lower it.

Diaphragm fill valve (plastic)

The difference between this fill valve and one above is that it has a diaphragm cover made of plastic rather than brass.

Bending the brass rod (up or down) or turning the adjusting screw at the top of the diaphragm cover is all you need to do to change the level of water in the tank.

A counterclockwise turn of this crew raises the level of water while a clockwise turn lowers it.

Float-cup fill valve

This fill valve has two methods of changing the level of water in the toilet tank one of which entails turning a screw mechanism in one direction or the other.

For the majority of these valves, however, there’s a metal spring clip which you can pinch and move upwards to raise the level and downwards to lower it.

Pressure-activated fill valve

For the pressure-activated fill valve, you turn an adjustment screw at the top in a clockwise manner to raise the water level and counterclockwise to lower it.

Internal float fill valve

Given that the whole fill valve and its mechanisms are enclosed in the valve head, you first give it a counterclockwise turn to release it then either raise or lower it to raise or lower the water level respectively. After that, you turn it in a clockwise direction, lock it into place.

At times, the reason for having too little water in the toilet tank may be a punctured floater ball which will require replacement. When adjusting these levels, keep an eye on the recommended water levels marked inside the tank to prevent having too little or too much water in it.

Water Wastage

Calibrate the fill valve and the flush valve so as to send water into the toilet bowl; the fill valves opens the intake to allow in water.

At the proper calibration, the tank and bowl should reach their fill lines at the same time. If not, the toilet may waste water as the inlet sends in water which goes directly to the bowl rather than filling up the tank.


To determine this issue, flush the toilet then observe. If the bowl stops filling before the tank, you’ll need to recalibrate the fill valve as in the methods stated in the previous point.

Constant Running of Water

When the flapper of the fill valve is faulty, you could hear the water filling the toilet tank continuously. The problem is that it can’t completely close the outlet to the toilet bowl. As such, the water keeps flowing from the tank to the bowl with the inlet remaining open to maintain a certain level.

The cause of this issue is usually a worn out or damaged flapper or other part such as a stuck flapper chain or flush handle.


The solution to this is to release the stuck part be it the flapper, flapper chain or handle. If the flapper is damaged or worn out, you’ll need to replace it altogether.

Float Issues

The floating ball or other mechanism is one of the most important parts of the fill valve as it ensures the water level is always restored to a given point. When it doesn’t gauge the water level properly, your toilet won’t fill up correctly. It can be due to a stuck brass rod, punctured float ball, or a poorly adjusted float mechanism.


The solution to this issue depends on the problem you have. If the floater is stuck, you’ll need to release it to its normal working condition. If the floater is punctured, you’ll need a new one. For a poorly adjusted float mechanism, you’ll use the solutions in point 1 above to readjust it.

Clogs in the Fill Valve

The fill valve’s mechanisms are quite sensitive to the nature of the water flowing into and out of the toilet tank. If there’s dirt in it, it could easily lead to a clog that may partially or fully block the flow of water into and out of the tank. The clogs can be a single blockage or the continuous buildup of debris on the fill valve parts.

The problem often presents itself as an irregular flow of water such as a constant flow, slow flow, hissing sound, or stuttered flow. In some cases, the flow may be completely inhibited leading to an empty tank.


To unblock fill valve clogs, you need to first identify the actual location and type of blockage. You can easily identify the area of blockage as it’s a small setup. You then open the valve up and simply poke out the blockage.


Fill valves tend to leak when there’s an issue preventing them from closing the water inlets and outlets completely. For example, the clogs previously mentioned may make it impossible for the fill valve to be completely closed. As such, water keeps on flowing into the tank and consequently into the bowl.


The same solution used in eliminating clogs from the fill valve will be used here. If the issue is a worn out or damaged flapper, you’ll need a new one.

Dirty Water Back-Siphoning

Toilet water is contaminated and shouldn’t mix with drinking water even when the inlet is the same. If you don’t have a non-siphon fill valve, you’re likely to experience back-flow from the tank into the drinking water whenever there’s a drop in the pressure. This occurs when you have a siphon or submerged inlet fill valve.


The only solution to this issue is getting a non-siphon fill valve. Today, most houses are built ready with a non-siphon fill valve for all toilets.

Stuck Parts

When the fill valve parts get stuck, you’re likely to experience issues such as hissing sounds, too much or too little water in the tank among many others. Among the parts likely to get stuck are the diaphragm in a brass diaphragm fill valve, the O-ring of a piston/plunger fill valve, and the flapper.


For a stuck diaphragm, add penetrating oil at its top then work the brass rod up and down. The diaphragm will move up and down as well.

With repeated motions and enough penetrating oil, the diaphragm will come loose and work fine. Employ the same process is for a stuck O-ring. For a stuck flapper, scrap off the sediments or other items to restore its working condition.

Broken Parts

Fill valve parts are mainly made out of plastic and brass. While both materials are quite durable as they do little work, they eventually wear out and will often break.

While plastic parts will become brittle and break off, brass parts tend to rust due to the minerals in the water and also break off in the end.


The solution to a broken part is simply replacing it at once. That also goes for punctured or damaged parts.

Malfunctioning Pressure-Sensor

In the pressure-activated fill valve, there’s a pressure-sensor at the base of the toilet tank that ensures that water is maintained at a given point. This eliminates the need for a floating mechanism and uses less space.

If this pressure-sensor malfunctions, there will be problems with how much water the tank will have.


The best solution in this case is getting a new pressure sensor or fill valve if the need arises. Ensure that it’s actually malfunctioning and not just a case of not being adjusted properly.

These issues can be solved as stated above with care being taken to only attempt solving something you’re confident with. Most solutions are simple DIY projects not needing any expertise.

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