A well-foot valve is essential to any well-pumping system, as it maintains priming and prevents pump damage. A pump that has not been primed can rapidly overheat and fail. The foot valve, which is affixed to the suction line’s intake, effectively restricts the return of water to the well, thus ensuring that the pump remains primed. This article covers the operating principle, construction, and installation of well-foot valves.

Well-foot Valve Operating Principle

A foot valve functions in a way related to a check valve, permitting the unidirectional flow of media while closing in the event of backflow. When the well pump is turned on, water in the suction line flows toward the pump, forming a vacuum at the foot valve outlet. A suction is generated by the vacuum, which draws water from the well through the valve and to the pump.

The water in the suction line reverses direction and returns to the foot valve when the pump is deactivated. To prevent the column of water from re-entering the well, the foot valve is closed by the backflow pressure.

An essential component of a well-foot valve is the strainer affixed to its inlet port. This filter effectively obstructs the ingress of sizable debris that could damage or jam the valve.

Check valves are unnecessary for systems less than 8 meters in depth. More in-depth well systems utilize check valves to alleviate pressure on the foot valve during periods of pump inactivity.

Components and Features of Well Foot Valve

For simple installation, standard foot valves feature self-tapping male or female threads. The universal foot valve design consists of the following four fundamental components:

A strainer or screen:

The screen prevents sediments, detritus, and other solid particles from entering the valve.

Disc:

When the pump is in operation, this door or gateway of the foot valve opens, permitting media to enter. Discs are frequently crafted from durable materials such as brass, bronze, or steel to ensure longevity.

Body:

This vital component contains the foot valve’s complete valve mechanism. The body may be brass, plastic, bronze, or stainless steel.

Seat:

A body component equipped with rubber or silicon o-rings that seal the valve and prevent leakage when the pump is turned off. During a pump malfunction, the valve disc is supported by the seat. The seat is vulnerable to deterioration caused by sediment or high-velocity media that traverse it.

Design of Well-Foot Valve

The five varieties of foot valves are spring, flapper, ball (with or without a spring), and membrane.

· type of ball with spring:

A spring maintains a spherical ball affixed to the valve seat with the valve closed. The optimal fluid for this form of foot valve is effluent and viscous substances.

· Ball type without spring:

An O-ring perch supports a ball. The flow through the valve propels the ball from the seat into a side chamber. As the flow decreases, the object returns to the seat. This valve is appropriate for applications involving minimal pressure.

· Membrane type:

The strainer of the valve contains a polymer membrane that prevents water from entering. The liquid can pass through the valve because the membrane is displaced during pump operation and vacuum. The membrane returns to its initial position upon cessation of vacuum, thereby closing the valve.

. Spring-shaped:

This variety of foot valves consists of a poppet and spring. When the valve is closed, the spring retains the poppet in contact with the chamber. Any orientation is viable for installation.

· Flapper type:

The valve seat supports a hinged, flat disc. Upon pump activation and subsequent reduction in vacuum line pressure, the flow through the valve propels the disc open. When the compressor is deactivated, the valve is closed by backflow. Since gravity is required for the proper functioning of this valve, implementation in any orientation is not feasible.

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Why Is a Strainer Required for Well-Foot Valves?

A foot valve contains a strainer that is an important part of it. It is typical for a foot valve’s suction line to get clogged because it is used in ponds, wells, and pools. A foot valve strainer screens out big pieces of trash, grit, or solids that could come up through the suction line and damage the pump by blocking or jamming the foot valve.

Moreover, plastic, brass, or stainless steel are used to make filters. Plastic strainers are used for small tanks and other light-duty tasks. Heavy-duty strainers are made of stainless steel or brass.

How to Clean the Strainer in the Foot Valve?

Most foot valves have strainers that users need to clean. But some pumps have strainers that clean themselves. In these pumps, special pipes bring a small amount of super-pressurized liquid (like water) back to the filter. After that, the liquid is sent to a set of special tubes. Up and down, the liquid shoots out of the strainer. The screen keeps turning because of this spraying. This causes any debris that links it to blow off the screen and away from the suction line.

Foot Valves Properties:

Foot valves, instead of standard check valves, are equipped with a strainer or filter receptacle that prevents residue from entering the pump while permitting pure water or any other liquid to pass through. Various particle diameters are available for the basket, which facilitates replacement and cleaning and is detachable, contingent upon the type of liquid being circulated. In addition, the valve is equipped with a rubber membrane or seal that tightly encircles the basket and prevents leakage.

Well-foot Valve: Types of Connections

Foot valves have two main connections: threaded and flanged.

Threaded Connection

One main difference between foot valves and check valves is that foot valves only have threading on the side that allows air out. One side of the intake has a screen. There are three kinds of thread.

• Female: It has threads inside to join pipes with outside threads.
• Male: It has threads on the outside that are linked to pipes with threads on the inside.
• Dual: Threading on both the inside and the outside so it can join any pipe threading.

Flanged Connection

Flanged links work better in high-pressure manufacturing settings. Two popular types of foot valves are ANSI 125 and 150.

• ANSI 150: Flanges made of ductile iron, steel, or stainless steel that can handle about 150 psi at 600 °F (10.3 bar at 315 °C).
• ANSI 125: Flanges made of cast iron that can handle 125 psi at 353 °F (8.6 bar at 178 °C).

Please read our complete list of the check valve

Well-Foot Valve Flow Systems

Foot valves are comprised of three distinct flow systems, each of which is optimal for a particular application.

High-flow system foot valves

The high-flow system foot valves are designed to endure high pumping rates and deep wells. They are utilized on wells with a size of at least 2 inches.

Low-flow system foot valves

Low-flow system foot valves are utilized in small-diameter piezometers that raise 100 feet of water.

Microflow system foot valves

Microflow system foot valves are utilized in micro-wells that employ direct push technology, a method for subsurface soil investigation. Most of these valves, constructed primarily stainless steel, are made of FEP (Florotherm) or HDPE (high-density polyethylene) tubing.

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Materials for Manufacturing the Well-foot Valve

The foot valve is immersed in water throughout its entire operational lifespan. The material selected must, therefore, be resistant to rust and corrosion. Foot valves are frequently constructed from PVC, stainless steel, heavy-duty cast iron, and bronze.

Metallic materials are more appropriate for applications involving intense pressure. However, PVC can withstand internal pressures of up to 1218 psi or 84 bar. Additionally, PVC is non-corrosive; therefore, it is preferable to use PVC foot valves when the application’s system pressure falls within the stated pressure rating.

Well-Foot Valve Installation

Foot valves are suitable for narrow and deep wells, irrespective of whether a two-line or single-line hydraulic pump works. Submersible pumps also incorporate check valves.

• Ensure the foot valve is sized appropriately for the flow conditions, not the conduit size, before installing the suitable foot valve. Flow rates below 1.5 meters per second are optimal for foot valve operation. An increase in velocity may result in cavitation of the foot valve, which may fail early.
• Consider the pressure of the entire system, not just the pressure setting of the pump.
• Eliminate accumulated sediment. Use high-pressure water to force residue from the well’s bottom to the surface. Wait for the water to become clean before proceeding.
• Before using the foot valve, ensure that no extraneous objects are inside the valve, including metal fragments, welding residue, or pipe scale. These may impede the disc’s motion and harm the disc or seating.

During the installation of the well-foot valve:

• While installing the well-foot valve, ensure that the arrow indicates the direction of water flow (up).
• Vertically position the foot valve during installation.
• The foot valve should be positioned no lower than 25 vertical feet (7.6 meters) below the pump’s inlet for shallow wells.
• Check valves must be implemented in deep wells that utilize submersible pumps to mitigate the strain on the foot valve. Approximately six meters should separate the first check valve from the pump, and a check valve should be installed every 60 meters of piping after that.
• It is imperative to position the screen 3 to 6 meters below the minimum pumping level, which denotes the lowest point where waterfalls occur while the pump operates, not at the bottom of the well.

How to Use a Foot Valve?

Installing a foot valve in the inlet end of an underwater pump system is the right way to use one. Occasionally, cleaning or replacing the strainer or filter basket is needed to keep the fluid flow going smoothly. A level installation and priming of the valve before use are also necessary. It is suggested that a filter with twice the inlet size be placed with the valve to ensure no flow restrictions.

Well-Foot Valve Issues

A problem with the foot valve is not always the cause of a pump losing water flow. Additionally, the pipe between the valve and the pump may be broken, allowing air to enter the flow. But because everything is beneath, these problems must be fixed by pulling up the pipes and foot switch.

Three problems often occur with foot valves: wire drawing, disc flutter, and sediment buildup in the screen. Repairing the first two problems requires a foot valve, but the third problem can be fixed without separating the pipes. So, the first thing that might be best is to try to fix the problem of water buildup.

Disc flutter

Because it wears out too quickly, disc flutter occurs when a foot valve is used at a small fraction of its full capacity. This problem can be lessened by carefully picking the smallest valve that can handle the flow of the media.

Sediment buildup on screen

One common way to keep the foot valve screen from getting too full of dirt is to “sudden” the well. Two preventative steps you can take are to use a surge block or a bailer.

• Bailer: A bailer is a check valve lowered into a well to collect water and dirt and then raised to the surface to be emptied. The well is being developed slowly, but in the end, much dirt will be removed from the area where the foot valve will be.
• Compressed air: If the foot valve is already in the well, this is a third way to raise the water level. Compressed air is pumped into the well to raise the water level. Once the water level hits the well casing’s top, the air is turned off to drop the water level quickly. This motion is not as safe as a surge block and might shake some dirt out of the foot valve.
• Surge block: A surge block over the foot valve and fits like a cover. It looks like a donut. The surge block cuts down on the space between the well pipe and the opening. Later, the well pipe can be moved up and down several times, like a plunger. It’s easier to do downward steps when some of the water is going into the pipes. Over time, this may shake some or all of the dirt on the screen free.

Wire drawing

Wire drawing happens when water that moves quickly or dirt runs past a rubber valve seat. The seat gets a groove over time. The gap stays when the valve closes, and small amounts pass through it, which causes pressure creep (an increase in exit pressure). Run a tap tied to the well to stop the pressure from creeping up. On the other hand, systems that run less often can have bigger problems.

Use a stainless steel seat to keep from drawing wires. Pick the most miniature foot valve that can handle the fuel flow through the system. Smaller valves open wider, keeping sediment away from the seat and slowing down the flow through the valve.

Well Foot Valve Maintenance

Once you have lifted a foot valve out of a well, take the time to take it apart and see what can be fixed inside. Before you do this, check with the maker to see if taking the valve apart will stop the assurance.

Taking apart a foot valve is a simple process. Take off the disc first, then the screen and seat. After taking out the disc:

• Check to see if the inside of the valve is clean.
• Use white vinegar to remove the scale built up on the stem and stem controller.
• Check whether the stem or guides have any circular wear. If there is, change one or both of them.
• Make sure there is no blockage in the flow path.

Well-Foot Valve Applications

Foot valves can be used in lakes, rivers, ponds, and other water sources besides water wells. But if you’re not using a well, you should build a valve stand so the foot valve doesn’t rest on the bottom. Foot valves are also used in industrial sump pumps, river and lake intake pumps, and the air brake lines of work trucks.

Pros of A Well-Foot Valve

Some say small wells (less than 4 meters) don’t need a foot valve. Unprimed pumps can make a vacuum and pull up about 2 to 4 meters of water from the well. Most pumps can run dry for 45 seconds before they break, but this can get water into the pump before that time.

Foot valves cannot completely protect a pump from damage because they are not the only parts that can break. However, well-foot valves are easy to set up and provide extra security against air entering the pipes, which can lead to cavitation.

FAQs about Well Foot Valve

Do you need a well-foot valve?

Foot valves are needed to keep the pump primed in wells deeper than 4 meters. If you run a dry pump, it will get broken quickly. Foot valves are also a good idea for small wells.

How do you make sure a foot valve works?

Because you can’t see a foot valve without pulling it out, it’s hard to tell if it works. But if the well pump doesn’t stay charged, the pipes or the foot valve are broken and must be fixed.

What’s the difference between a check valve and a foot valve?

While a foot valve only has a thread on one side and a screen on the other, both sides of a check valve are threaded.

Conclusion:

Foot valves are an important part of any underwater pumping system because they keep the flow of liquid steady and keep the pump from breaking. We hope this guide has provided helpful information about foot valves, their work, and what they can be used for. If you have more questions, don’t hesitate to contact Plumberstar. Remember that a properly installed and kept foot valve can make all the difference in how well and reliably your pumping system works.