Float Valve

Float Valve

What is a Float Valve ?

Introduction to Float Valve / Ballcock Valve

Ballcock valve is used to maintain fluid level in a storage tank or a sump. Ballcock Valves are also known as Float Valve or Ball Tap. As the name indicate it consists of a ball shaped float which sense the current level of the fluid and actuate the valve to open or close depending on the fluid level.

As shown in below figure a hollow air filled cylindrical, spherical, oblong or similarly shaped container called 'float' made metal or polymer connected to a piston operated valve using a long lever called float arm. The float am can be a flat rectangular or cylindrical in cross section. The valve used in a ballcock valve is a flow isolator valve can be of a piston operated or a diaphragm operated valve and the actuator mechanism use the float position to open and close the valve to fill the tank.

Types of Float Valve

Types of Float Valves / Ballcock Valve

Different types of ballcock/float valves are available in market based on fitting orientation,use,working principle,size etc.

Horizontal and Vertical float Valves

  1. Vertical Float Valve

Here the float is oriented and moves in vertical direction as shown in figure. The float is directly or indirectly act on the valve seat for closing and opening the valve. The force of buoyancy is directly acting on the  seating area. The buoyancy force should be higher than the effective force due to inlet pressure for fully closing requirement of valve, So the float size is depends on the inlet pipe pressure,the more the inlet pressure higher the float size required. Vertical float valves are most suited in deep tanks/sumps where the horizontal spacing is limited mainly in industrial application like oil and chemical industry tanks for automatic shut off/filling operation.

  1. Horizontal Float Valve

Horizontal float valve is works based on the principle of force of buoyancy and principle of lever and fulcrum. As shown in figure below. Float arm acts as a lever and pivoted on body act as a fulcrum. The buoyancy force exerted on the float is transferred to the valve seating by the lever which gives more effective force on valve seating, so the more  lengthier the float arm, smaller the required float size.


Application of Float Valve

Water Supply

Float valves are widely used in water supply system to automatically fill the tank or sump from a main storage tank.  It can employ directly in by installing directly  inside the tank/sump or by using as remote sensing valve for the main valve.  


All toilet flush tanks are employed with float valve  for filling the tank after each flush.  


Float valves are widely used in oil,chemical,petrochemical factories for automatic filling of liquid tanks. 

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Working of a Ballcock Valve

Working principle float is based on buoyancy. The buoyancy force exerted on the float is used as the seating pressure to keep the valve in closed condition.  

Below figures show the working  of a piston operated ballcock valve/float valve open and closed condition.  As shown in figure one end of the float arm is connected to the cylindrical or spherical float and other end is connected to the piston which can slide in the body bore. The float arm is pivoted in the body extension. The ballcock valve body is connected to a inlet pipe having a continuous flow of fluid at desired pressure. The fluid entered from the inlet pipe and flow through the nozzle to the tank. is provided to ensure a tight seating of piston.  

  1. Closed Condition

When the liquid level in the tank is at the desired or specified level as shown in figure, the float will be at top most position and this keeps the piston closed against the nozzle tightly. This stops the continuous flow to the tank.

  1. Open Condition

When the fluid level in the tank/sump goes down due to the fluid usage, the float also moves down. Since the float lever is pivoted, the top end along with the piston moves up. This in turn create gap between sealing and nozzle and fluid start flowing to tank fluid level rise up till the float reaches the old level to close the valve.