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What is a Foot Valve, and How Does It Work?

Foot valve with a strainer

The foot valve is a crucial component of air and liquid suction systems. Being a one-way valve, it helps prevent a reverse flow of media and keeps such systems working as they should. In this article, you’ll learn everything about this type of valve.

What is a Foot Valve?

A foot valve is a check valve (no return valve) that prevents reverse flow in the pipes of suction pumps. As such, you will usually find it installed on the pick-up or intake end of these pipes and hoses.

The typical foot check valve has a mechanism that can only open one way and relies on the suction force and back pressure to work.

Usually, the valve comes with a sieve attached to the inlet or suction side. The sieve traps solid particles, protecting the suction from clogging problems. By carefully selecting the suitable material, you can use the valve with these types of media:

Foot valve diagram showing its internal construction
Foot valve diagram showing its internal construction
Resource: https://www.youtube.com/watch?v=dE8PtJhgp3k

What Does a Foot Valve Do?

A foot valve prevents media from flowing back down a pipe (or hose) after the pump shuts down. It also keeps water in the suction line when the pump is not running. By doing so, the valve ensures the following:

  • That the pumping system is always primed and does not need priming when the pump starts
  • That the pump doesn’t run dry and risk getting damaged

Some uses of the valve (such as draining ponds or pumping water out of wells) may involve sediment and other debris, so it usually comes with a filter affixed to the inlet.

Using a foot valve with a strainer or sieve ensures solid particles that may clog the valve and suction do not get in with the water. If no sieve is present, using one is recommended if the application demands it.

Different foot valve parts
Different foot valve parts
Resource: https://www.mdpi.com

Foot Valve Parts

The typical foot check valve consists of these critical components: the on/off part, the seat, the body, and, most often, a strainer or sieve.

  • On/Off Component: this part opens the valve. It can be a ball, poppet, membrane, or disc made from various materials such as brass, bronze, or steel.
  • Seat: the seat, which can be rubber or silicone, seals the valve off when closed, preventing media from leaking.
  • Body: the body contains all internal parts, including the ports, disc, and seat. It can be many different materials, such as stainless steel, brass, bronze, cast iron, or plastic.
  • Strainer: the strainer is a metal or plastic sieve. It helps filter debris and prevents clogging or other damage.

Depending on the design, other foot valve parts may include:

Foot valve working illustrated
Foot valve working illustrated
Resource: https://www.youtube.com/watch?v=xLXnQmwHKPs

How Does A Foot Valve Work?

Now that we understand the parts that make it and its function let’s see how a foot valve works. As earlier mentioned, it’s simply a check valve that often comes with a sieve or strainer.

When used in a plumbing system, it relies on suction, backpressure, or gravity. The following sequence describes its working.

  • The suction pump comes on
  • Suction pressure causes the valve to open, either by moving a membrane, ball, or poppet
  • Water flows through, and large such as sediments and other debris are trapped by the sieve
  • When the pump stops, water pressure is no longer working on the valve mechanism
  • A reverse operation happens. Water starts to flow down the suction pipe
  • The valve closes under the force of water assisted by gravity or return spring
  • Water remains in the suction column, helping to keep it primed

Foot Valve Types

Foot valves are available in different designs. These include opening and closing mechanisms like floating balls and spring-loaded discs or membranes.

Most often, manufacturers classify them by their materials. In that regard, we have the following types of foot valves: brass, stainless steel, cast iron, and plastic.

Brass Foot Valve

Brass is a resilient material that you can use in various settings. A brass type of valve will resist corrosion, is safe to use in water applications, and has several other benefits, such as cost-effectiveness, given their versatility and long life.

Stainless Steel Foot Valve

A stainless steel type offers an excellent ability to withstand corrosion resistance, safety in drinking water systems, and longevity. You can use this type of valve in high heat and pressure systems since the material can withstand that.

Cast Iron Foot Valve

Made by mixing iron with carbon and some silicon, the cast iron type is rigid and rated high for heat resistance. It’s also a low-cost option. On the downside, cast iron valves are brittle and may crack if bent. They can also rust and are best with non-corrosive media like air and gas.

Plastic Foot Valve

A plastic foot valve is lightweight, affordable, and will not rust or corrode if exposed to different materials and operating conditions. You can use them with various media, including the corrosive types, from water and gas to oil and industrial chemicals.

Foot valve for water pump
Foot valve for water pump
Resource: https://youtu.be/nhx_deZq7DY?si=TcoTPWcM3-HnY3Zb

What is a Foot Valve Used For?

A foot or suction check valve prevents media from flowing back. That means situations such as water extraction from tanks and wells, the draining systems of pools and ponds, or car pressure-washing equipment. Some of its common uses are:

Water Pump

These valves are standard anywhere a pump raises water or other media to a higher level, such as pressure washers. The foot valves provided in pumps are of this type. They use the mechanism we described earlier: a one-way opening mechanism and a sieve for debris.

Water Tank

A pumping system is necessary to raise water from an underground or other tank. This pump requires a one-way check valve at the suction end of the hose or pipe. The valve will prevent the reverse water flow while filtering out debris to protect the suction system.

Underground well

If you have an underground well, you probably need a pump to extract water from it—and a foot valve to prevent water from flowing back when the pump stops working. A foot valve for well water extraction keeps the system primed, protecting the pump from damage.

Brake Foot Valve

The foot valve also finds use in the air brakes of motor vehicles. Large tracks commonly use this type of braking system. The foot valve for this application uses the working principle of the conventional kind, acting as a non-return valve or check valve.

Conclusion

The foot valve is a check or non-return valve used in pumping systems, often including a sieve to block particles. Available in different designs, materials, and sizes, this valve gives you a broad range of options for your specific application or project needs.

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