5 Types Of Toilet Overflow Tube Valves

There are several types of toilet overflow tube valves in the market, but even if there are, they have more or less similar mechanisms and work processes. These valves play a significant role in the toilet flushing mechanism.

We will talk about how a toilet overflow tube works, why it is crucial for the flush system, what types of fill valves you can use in the flush tank, and their uses and advantages.

So, if you are remodeling your house or just trying to replace the broken fill valve system in your toilet tank, stick together because we will cover those parts as well.

5 Types Of Toilet Overflow Tube Valves

Before heading to find out the valve types, first, get to know what an overflow tube does.

What Is A Toilet Overflow Tube?

Toilet overflow tubes are inarguably one of the most significant parts of a flush toilet. The overflow tube is a vertical tube that has a connection with the fill valve through the fill tube. It flows excess water into the bowl in case the float ball fails to stop entering water into the tank after a certain level.

Function Of A Toilet Overflow Tube

When you press the flush button, the attached chain pulls the flush valve. As soon as the flush valve opens, the water runs into the bowl. So, there is a low water level in the tank. Now, the tank refills from the water supply through the fill valve.

When it refills and reaches a certain level, some water passes to the bowl from the overflow tube to keep the water at a safe level and prevent overflow. The overflow tube passes the excess water into the toilet bowl. That is how the toilet bowl always has water in it.

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Based on different types of toilet fill valves, people look for the types of overflow tubes. So, let’s have a look at the fill valve systems types.

Types Of Toilet Fill Valve Systems

Like the overflow tube supplies excess water, the fill valve stops the water intake when the water level reaches a certain point. There may be numerous types of fill valves on the market. However, the most common types of toilet fill valves are as below with their benefits and short description.

i) Piston Or Plunger Type Fill Valve

Piston or plunger fill valves have another name, ballcock fill valve.  These types of fill valves generally have a metal (brass/copper) construction, but they may have a plastic ball.

Plunger fill valves are the most common in old model toilets and possibly the oldest type used in the toilet tanks. Therefore, they are more suitable for old model tanks. However, they are still available in the market even though they are no longer compatible with the modern toilet system.

The system has a vertical tube, also known as a fill tube which releases water. The tube is connected with a ball that floats when the water fills up the tank and closes the valve. And when the tank gets empty, the floating ball lowers, the washer at the top of the fill valve loosens, and water comes in.

ii) Metal Diaphragm Fill Valve

The diaphragm-type fill valve has a design like the human diaphragm in addition to a metal cup on top as the float ball. When water pressure from the fill valve comes, the diaphragm lifts off the top and fills the tank. In this model

In the older models, brass was a common material. Both the body and the cap were of brass. Since metal has a tendency to rust, these models of fill valves were useless after a specific time. Therefore, one had to replace the valve after a while. However, the cast brass fill valves are no longer in use these days.

iii) Plastic Diaphragm Fill Valve

The plastic diaphragm fill valves are more common in tanks nowadays than the older versions of metal valves. They are relatively cheaper and long-lasting. Here, instead of the plunger or piston valve, a seal inside the fill valve closes by the float cap when the tank is filled.

They have a similar design to the metal one. However, these have a plastic construction, generally with PVC. Plastic does not rust like metal over time. However, the problem with plastic fill valves is that they tend to weaken when contacted with chlorinated water.

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iv) Floatless Fill Valve

The float less model of the fill valve does not have a floating ball but rather a diaphragm that can sense the water pressure. The pressure valve shuts off or closes when the water reaches the maximum point. These are cheap yet better alternatives for the other type of fill valves.

Developed in the ’90s, this type of fill valve is suitable for low-profile, eco-friendly toilets where the tank size is relatively small and requires less water to flush. The earlier version had a health hazard since it pushed some water back into the water supply.

v) Float Cup Style Fill Valve

The float cup fill valves are more common in the modern-day toilet system and toilet repair kits. Developed in the ’50s, it is an anti-siphon fill valve. In this fill valve system, a cup moves vertically around a tube as the water level increases or decreases.

A controllable metal spring connects with the floating cup with a rod. You can change the spring length if you want to change the water level inside the tank. Also, the adjustable shaft makes it adaptable in various tank sizes. So, the float cup fill valves are often chosen as a replacement for plunge or diaphragm-type toilet fill valves.

How Do You Adjust A Toilet Fill Valve?

In the toilet tank, the water level should align with the watermark line. If the water level is too high than the watermark line, the toilet might constantly run, bypassing the excess water through the overflow tube. And if the water level is too low, the toilet may not flush the bowl efficiently enough.

To adjust the toilet fill valve, you need to empty the tank. You must consider where the waterline mark is. You can flush the toilet or lift up the flush valve to do so. The fill valve float drops and relieves pressure on the float and the adjustable screw. The floatless fill valve is now ready for adjustment.

Now, turn the adjusting screw counterclockwise if the water level in the tank is too high. And if it is too low, turn it clockwise. You have to be prompt here before the tank refills. Once the fill valve shuts off and stops refilling, check where the water level resides. Make necessary adjustments if required.

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Frequently Asked Questions (FAQs)

What Does The Overflow Tube Do In A Toilet?

An overflow tube in the toilet tank prevents any excess water from spilling over the tank. The excess water runs through the overflow tube into the bowl and thus prevents it from overflowing.

Do All Toilets Have An Overflow Pipe?

All toilets may not have an overflow pipe. However, all modern toilets have an overflow tube integrated with the flush valve inside the toilet tank.


Even though there may not be many types of toilet overflow tube fill valves, you will certainly find variations in the fill valves. Therefore, choose the type that is more compatible with your toilet cistern water supply system and local building code.

It is better to pick the PVC fill valves over the metal ones since they will last longer without nullifying the system. And you can always opt for professional help if it seems bothersome to you to choose and replace the fill valve system.

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