What is a foot valve and what are its uses

What is a Foot Valve?

A foot valve is a type of non-return valve, with strainers mounted at the open end of the pump suction pipelines. Foot valves are used when the pump has negative suction. These valves are placed at the pumps wet well. The flow area of the foot valves is larger than the pipe size, so there is only less head-loss. Foot valves are known for their ability to keep the continuous presence of suction within the pump. A foot valve is a special design of the lift check valve. These valves are designed for up-flow and are attached to the bottom of a pump suction pipe. Foot valves can cause leakage, when they are used with fluids that have solids, and they are difficult to service. Foot valves would decrease the net positive suction head available.

Why do you need a strainer for a foot valve ?

Strainers are used to protect the valves it will prevent the accumulation of debris, the debris could jam the foot valve, and it could damage the pump. So strainers are an important part of a foot valve.

What are the functions of the foot valve ?

The basic function of a foot valve is to prevent water from flowing back down the pipe. It can also be described as a foot valve that would only allow the pump to pull water up but does not allow the water to flow back down.

What are the parts of the foot valve?

What are the features of the foot valve ?

Most of the foot valves have self-tapping male and female threads for easy installation. Internal balls for quick sealing and valve reaction, and has the flexibility to fit various types of water pump uses, such as well development and volatile organic compounds sampling and purging. Foot valves are cheaper when compared to other valves. Mostly foot valves are made up of heavy-duty cast iron and bronze, as well as PVC. So that they would last longer when submerged in water.

What are the uses of the foot valve ?

Foot valves can prevent the pump column from draining upon pump shutdown, these valves are widely used in all kinds of pneumatic system. They are used in a suction line of the pipeline as well. Positive sealing action is provided in both low and high pressure without slamming. The foot valve offers spring load closing and can be installed in any direction. Foot valves have low head-loss. Foot valves can maintain hydraulic pressure.

How foot valves are constructed ?

Foot valves are either made of stainless steel or PVC plastic. Foot valves are able to keep the suction continuously in the pump. Because of the larger flow area, the head-loss is very less. Foot valves usually come with surge blocks. Surge blocks will press the valve body so that the residues can be removed and by this, the flow of water would very easy. These valves are expanded by the help of surge block. There are instances where the pressure can actually pop the valve out and causes major leakage, thus it is important to use the right kind of material in the tubing to be able to support the force within the valve.

How does a foot valve work ?

Most foot valves are fitted with inlet strainer, and they filter the incoming water and prevents the valve damage. Electric pumps are used to pump water from a lower level to higher level and this would require a lot of energy, the could flow back to the source from the higher level to the lower level if the pump is turned off the suction is gone and the water will flow in the reverse direction due to the gravity, it can be prevented by using foot valves. Foot valves are used to prevent the backward flow of water through the pipe when the water pump is turned off, thus the column of the water in the pipe is maintained and all the issues are resolved. A foot valve is a kind of check valve, and they only open in one direction so the foot valves would only allow a unidirectional flow and it will close off when the direction of flow is reversed.

Working Principle of Foot valve

Foot valves are placed in the pick-up end of the pipe so they are located at the very bottom. In order to pick the water from a lower level pump is used and the pump will create suction and the water is pulled from the lower level, due to the upward pressure the foot valves open. When the pump is turned off the pulling force is removed and water will flow downwards due to the gravitational pull and foot valves blocks the downward flow of water. So the foot valve is a necessary part of the pumping system.

A foot valve is a type of lift check valve typically installed with suction strainers in the suction line. Its main function is to prevent the suction line from emptying when the pump is stopped (also see Valve). The foot valve should be positioned to maintain an appropriate distance between the valve, the pump sump floor, and the lowest suction-side water level. A commonly used type is the cup valve, known for its favorable flow characteristics (see Head losses).

What are the types of the foot valve ?

Membrane foot valve

These valves have a cylindrical rubber membrane fitted inside a steel strainer. If suction is formed in the strainer, then the membrane will be displaced, so that the fluid can flow through the valve. During the backflow the cylindrical membrane closes the apertures in the valve strainer thus the valve is closed.

Ball foot valve

In this type, a cylindrical inclined chamber and seating are used to guide the ball valve. Because of the inward flow, the ball will be displaced, along with its chamber, but when the flow rate decrease it runs down the chamber onto its seat. These valves are mostly used for contaminated water.

Foot valves are classified according to the flow system. Microflow system valves are used in direct push technology micro-wells and multilevel good installation. These are mostly made of stainless steel. Another one is high flow system valves, they are used on 2-inch wells or larger and can stand high pumping rates and very deep wells. The third type is the low flow system valves and is used in small diameter piezometers which lift up-to 100 feet of water.

Installation and Maintenance Tips for Foot Valves

Installation Guidelines for Foot Valves

• Ensure the valve is installed in a vertical position with the strainer at the bottom.
• Use thread sealant to prevent leaks during installation.
• Verify that the strainer is clear of any obstructions before placing the valve into the well or pipe.

Maintenance Considerations for Foot Valves

• Regularly inspect the strainer for debris buildup and clean it as needed to maintain optimal performance.
• Check the sealing mechanism periodically to ensure it is functioning correctly and replace any worn components.
• Monitor the valve for signs of wear or corrosion, especially in harsh environments.

Common Issues and Troubleshooting of the foot valve

Loss of Suction

A clogged strainer or a faulty sealing mechanism. Clean the strainer and inspect the internal components for damage.

Leakage

Worn or damaged seals, improper installation, or a cracked valve body. Replace seals, re-install the valve with proper sealing, or replace the valve if damaged.

Valve Sticking

Debris or scale buildup on the sealing surfaces. Disassemble the valve, clean the internal parts, and reassemble.

Advantages of Foot Valves

• Prevents pump priming issues by maintaining the water column in the pipe.
• Reduces the risk of pump cavitation.
• Cost-effective and easy to install in various systems.

Disadvantages of Foot Valves

• Can be prone to clogging in environments with high debris content.
• May require frequent maintenance in certain applications.
• Can cause a slight reduction in net positive suction head (NPSH) available.

Choosing the Right Foot Valve

Foot valves are essential in applications requiring one-way liquid flow, offering protection for water pumps and conserving energy, which extends the pump’s lifespan. Selecting a high-quality foot valve is crucial, as they can be difficult to access once installed.

PVC foot valves are generally a cost-effective and lightweight option suitable for most applications. However, when the application involves higher temperatures, pressures, or requires specific chemical resistance, metal options like brass or stainless steel are preferable.

Uses for Foot Valves

Foot valves, a type of check valve, are commonly used with pumps in both residential and industrial settings. They are designed to maintain pump priming by allowing liquid to flow in one direction, preventing backflow.

In residential applications, foot valves are often found in ponds, pools, wells, and other areas where pumps are used. In industrial settings, they are utilized in sump pumps, intake pumps for rivers and lakes, pneumatic brake lines in commercial trucks, and various other pump-related applications. These valves are just as effective in industrial environments as they are in a backyard pond.

Foot valves are equipped with screens that cover the valve opening, which can become clogged over time, especially in environments like wells or ponds. Regular cleaning of these valves is essential to ensure they continue to operate efficiently.

When to use a Foot Valve ?

Foot valves should be used whenever a pump requires a consistent flow of liquid and the prevention of backflow is critical. These valves are particularly useful in applications where the pump is situated above the liquid source, such as wells, ponds, and other water bodies. They are also essential in systems where maintaining pump priming is important to prevent the pump from losing suction and to ensure efficient operation.

Foot valves are commonly used in both residential and industrial settings. In residential settings, they are ideal for use in pools, ponds, and well systems to ensure a steady supply of water. In industrial applications, foot valves are used with sump pumps, intake pumps in rivers or lakes, and pneumatic systems, where maintaining a one-way flow is crucial for system efficiency and longevity.

Why are Foot Valves Needed?

Foot valves are essential because they prevent water pumps from running dry, which can cause significant damage, and they help conserve energy by maintaining the pump’s prime.

These valves are a critical component in all water pumping systems. For example, when pumping water from ground-level sumps to rooftop tanks, powerful electric pumps are required. These pumps create suction, forcing water upward through the piping system.

While the pump operates, a continuous column of water is maintained in the pipe due to the suction. However, when the pump is shut off, the suction stops, and gravity causes the water to flow back down the pipe. Without a foot valve, the water would return to its source, leaving the pipe empty and filled with air.

When the pump is turned on again, the air in the pipe resists the flow of water, preventing it from moving through the pipe. This situation can cause dry runs, which can damage the pump if not quickly resolved.

Foot valves effectively solve this issue by preventing backflow when the pump is off, ensuring that the pump remains primed and ready for the next use.

What are the applications of the foot valve ?

• Extraction of water from underground water wells
• Industrial
• Rural fire protection
• HVAC
• Irrigation
• Car wash system

To get more info about the other type of control valve refer the following link

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• Spool valve
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• Pinch valve
• Control valve calibration
• Plug valve
• Ball valve
• Gate valve
• Butterfly valve
• Globe valve
• Needle valve
• Diaphragm valve