How Does a Water Tank Float Valve Work

How Does a Water Tank Float Valve Work : DIY 7 Steps

Last Updated on May 10, 2023

Water tanks are an important part of many homes, but what happens when the water level gets too low, and the tank starts to run dry? When your water tank runs out of water, you might be wondering what happens. Will the pump turn off automatically? Will the house start to flood? The answer lies in the water tank float valve.

A float valve is a key part of any water tank system. This little device helps to regulate the water level in your tank by shutting off the supply when the tank is full or turning it on when the tank is empty. It’s an essential piece of equipment for keeping your home safe and your water supply steady.

Welcome to our blog on how a water tank float valve works. Here, we will provide an overview of how they work and the benefits they offer. So, read on!

How Does a Water Tank Float Valve Work : 6 Steps

Float Valves in Water Tanks How They Work
  1. A water tank float valve is a device that automatically regulates the level of water in a tank.
  2. The float valve consists of a float, a valve body, and a restrictor.
  3. The float is connected to the valve body by a rod or cable, and the restrictor is located between the float and the valve body.
  4. The function of the restrictor is to limit the movement of the float.
  5. The valve is usually installed at the top of the tank and consists of a float, a mechanism to open and close the valve, and a connection to the water supply.
  6. The float valve is often used in conjunction with a pump, and it works by automatically controlling the level of liquid in a tank or container. When the level of liquid rises, the float rises with it and closes the valve, preventing further liquid from entering the tank.
  7. The float then descends as the level of liquid falls, opening the valve and allowing more liquid to enter.  In this way, the float valve ensures that the tank always has a supply of water.
  8. As the water level decreases, the float lowers, and the valve closes. This prevents more water from entering the tank and keeps the level at a steady state.

What Are the Different Types of Water Tank Float Valves?

There are three main types of water tank float valves: the ball float valve, the diaphragm float valve, and the pilot-operated float valve.

Ball Float Valve:

A ball float valve is a type of valve that uses a ball-shaped mechanism to control the flow of liquid or gas. The ball float is attached to a lever, which is connected to a valve seat.

When the lever is actuated, the ball floats up and covers the valve seat, preventing further flow. Ball float valves are commonly used in plumbing and HVAC applications to regulate the flow of water or air.

They are also often used in industrial applications to control the flow of liquids or gasses. Ball float valves are simple in design and easy to operate, making them an ideal choice for many applications.

Diaphragm Float Valve:

A diaphragm float valve is a type of valve that uses a diaphragm to regulate the flow of liquid. The diaphragm is a flexible membrane that is attached to a movable arm.

When the liquid level in the tank reaches the level of the diaphragm, the arm begins to float. This causes the diaphragm to open, allowing liquid to flow into the tank.

As the tank fills up, the arm slowly sinks, and the diaphragm closes. This prevents further liquid from entering the tank. Diaphragm float valves are commonly used in water tanks and other applications where it is necessary to control the level of liquid.

Pilot-operated Float Valve:

A pilot-operated float valve is a valve that uses a small pilot stream of fluid to open and close a larger valve. The advantage of this type of valve is that it can be used to control the flow of liquids or gasses with very high pressures.

These valves are often used in applications where the fluid being controlled is very viscous or contains particles that could clog a regular valve.

One downside of pilot-operated float valves is that they can be more complex and expensive than other types of valves. As a result, they are typically only used in applications where their advantages outweigh their drawbacks.

Why Do We Need a Water Tank Float Valve?

Why Do We Need a Water Tank Float Valve

A water tank float valve is a vital component of any water tank, and there are a few reasons why.

  1. The float valve controls the level of water in the tank, ensuring that the pump always has enough water to operate.
  2. It helps to prevent overflow by automatically shutting off the pump when the water level is excessively high.
  3. It helps to ensure that the pump always has a consistent supply of water, even if the level in the tank fluctuates.
  4. It helps to prevent sediment from building up in the tank by keeping the water moving.
  5. It helps to prolong the life of the pump by providing a check against over-pumping.

All of these reasons highlight why a water tank float valve is such an important water tank component.

Different Parts of Float Valve:

Different Parts of Float Valve

To properly understand how a float valve works, you need to know the valve itself. A water tank float valve has three main parts.


A float connected to the float valve of a water tank is responsible for shutting off circulation into the tank when the water level reaches a certain point. The float is usually made of plastic or metal and is attached to a rod that extends into the tank.

When the water level changes, the float moves along with it and activates the valve, which then shuts off the flow of water. This prevents the tank from overflowing and ensures that there is always a consistent supply of water.

Floats are also used in toilets to regulate the volume of water that is flushed into the bowl. In this case, the float is usually attached to a lever that controls the flow of water.

As the water level in the bowl increases, the float ultimately triggers the lever, which then stops the flow of water. This helps to conserve water and prevent overflows.

Valve Body:

The valve body is the part of the float valve that regulates water flow into and out of the tank. It is usually made of brass or stainless steel and has a number of different ports that control the flow of water.

The most common type of valve body is the tee-type, which has two inlets and one outlet. The inlets are connected to the supply pipe, and the outlet is connected to the main pipe.

The tee-type valve body can be found on most residential float valves. The other type of valve body is the cross-type, which has one inlet and two outlets. The inlet is connected to the supply pipe, and the outlets are connected to the main pipe and the overflow pipe. The cross-type valve body is used in commercial float valves.


In a water tank float valve, the restrictor is designed to regulate the flow of water into the tank. By restricting the flow of water, the float valve can control the tank’s water level and prevent overflow.

The restrictor is an important component of the float valve system, and it is typically made from a durable material such as brass or stainless steel. Aside from regulating the flow of water, the restrictor also helps to protect the float valve from damage.

By controlling the amount of water that is allowed to enter the float valve, the restrictor can help increase the lifespan of the float valve and ensure that it remains in good working condition.

What Causes a Float Valve to Close?

There are several factors that can cause a float valve to close, including a rise in the level of liquid, a change in pressure, or a problem with the mechanism itself.

In most cases, a float valve will close when the liquid level gets too high, preventing the tank from overflowing. Float valves are also designed to close if there is a sudden drop in pressure, which can happen if pipe bursts or leaks.

Also, float valves can also be set to close if the temperature rises above a certain point, which is often used as a safety measure in process-control applications.

How Do You Test a Float Valve?

While float valves are typically very reliable, it is important to test them regularly for proper operation. There are two main ways to test a float valve: manually and with a pressure gauge.

  1. To test the valve manually, simply open and close the valve several times to see if the float moves smoothly. If the float is stuck or does not move smoothly, there may be an issue with the valve.
  2. To test the valve with a pressure gauge, attach the gauge to the inlet side of the valve and open the valve. The gauge should read between 20 and 40 psi. If the reading is outside of this range, the valve may need to be repaired.

Regular testing of float valves is essential to ensure that they are functioning properly.

How Do I Change a Tank Valve?

How Do I Change a Tank Valve

If you need to change a float valve, there are a few things you should keep in mind. Be sure to turn off the water supply before you begin. Use a wrench to loosen the lock nut that secures the valve to the tank.

Once the nut is loose, you can remove the old valve and replace it with a new one. Tighten the locknut and turn on the water supply. With a few simple steps, you can easily change a float valve.

Why is My Toilet Float Not Working?

Most toilets have a float mechanism that helps maintain water levels in the bowl. The float is usually a plastic ball that sits on top of the water. When the tank is full, the float rises and triggers a switch that turns off the water supply.

In any case, if the float is not working properly, it can cause the toilet tank to overflow or run constantly. There are a few different reasons why a float might not be working properly. The most common problem is that the float is stuck in the up position.

This can be caused by grit or particle build-up or by a leak in the air chamber that surrounds the float. If the float is locked up in the down position, it may be due to a faulty fill valve or a worn-out O-ring.

In either case, it is best to call a plumber for assistance. Trying to fix a toilet float yourself can be dangerous if you do not know what you are doing.

How Much Does it Cost to Buy Float Valves for Water Tanks?

While the cost of a new float valve will vary depending on the specific model and the retailer, it is generally between $10 and $50. You can review our list of affordable float valves for water tanks. There you can choose from a variety of valves based on your needs.

Replacing a float valve may not be a major expense, so you should choose the right one for your tanks that fit your budget. It is important to remember that the right features to look for, such as adjustable range, low-level alarm, and other features will make a big difference in your system’s performance.

So, Let’s Prevent Water Waste by Properly Using Water Tank Float Valves

After reading this article, you should have a good understanding of how float valves work and what factors to consider when choosing one. Thanks to its simple but effective design, the float valve is an essential aspect of any water tank assembly.
It’s important to understand when and how to replace it. A float valve is one of the most important parts of your water system, so be sure to keep a spare one in case of emergency. We hope you’ve found this article helpful and informative. Thanks for reading.

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