Foot Valves - Types and Applications
Figure 1: Foot valve
A foot valve is an essential component in submersible and jet pump systems, like wells. A submersible pump and a jet pump have the foot valve on their intake suction line. Foot valves prevent water from flowing backward when the pump is off and keep the pump primed at all times. This article explores the various types and applications of foot valves.
Table of contents
- What is a foot valve?
- Foot valve parts and features
- Strainer on a foot valve
- Foot valve maintenance tips
What is a foot valve?
Electric pumps are used to drive water from a lower level to a higher level. When the pump is turned off, the water may flow in the reverse direction due to gravity. One of the main functions of a foot valve is to prevent this reverse flow.
A foot valve is a non-return valve installed in a pump suction or at the bottom of pipelines to prevent water from flowing backward when the pump is off. The valve keeps the fluid trapped in the suction pipe when the pump stops, thus sustaining a suitable prime for the pump, and preventing pump burnout. When the pump restarts, suction opens the foot valve. The intake side of the foot valve has a screen that prevents larger debris from entering the valve and damaging the internal components.
Foot valves are commonly used in ponds, pools, wells, and almost anywhere there is a pump. The foot valve’s floor area or opening is larger than the pipe, thereby minimizing head loss (energy dissipated due to friction along the pipe length). Since the strainer or screen at the opening of the foot valve can get clogged with debris over time, especially in ponds, wells, and pools, it's essential to regularly check and clean the valve to ensure optimum performance.
Figure 2: Foot valve (left) and strainer (right).
Based on the internal configuration, there are different types of foot valves like membrane, ball, and spring types. For example, a spring foot valve opens when the pump operates, allowing the fluid to flow. When the pump is turned off, the spring closes the valve, stopping the fluid from flowing backward. Read our article on well foot valves for more details on the different foot valve types.
Foot valve parts and features
A typical foot valve has self-tapping male or female threads for easy installation. The universal design for foot valves has the following four basic parts:
- Screen or strainer: The screen keeps sediments, debris, and other solid particles out of the valve.
- Disc: This is the foot valve’s door or gateway that opens, allowing media to enter when the pump operates. Discs are commonly heavy-grade materials like bronze, steel, or brass to ensure longevity.
- Body: This is the essential part of the foot valve that houses the complete valve mechanism. The body can be cast iron, bronze, stainless steel, plastic, or brass.
- Seat: A part of the body that has o-rings made of rubber or silicon to prevent leakage when the pump is turned off and the valve is closed. The seat is where the valve disc rests when the pump isn't working. The seat is susceptible to wear from high-velocity media or sediment that flows past it.
Strainer on a foot valve
The strainer is an integral part of a foot valve. Due to its use in ponds, wells, and pools, a foot valve’s suction line is likely to clog. A foot valve strainer keeps out or filters large debris, sediments, or solid particles that may come up through the suction line and clog or jam the foot valve and damage the pump. Strainers are made from plastic, brass, or stainless steel. Plastic strainers are used in light-duty applications like small tanks. Stainless steel and brass strainers are ideal for heavy-duty uses.
Cleaning the strainer
For most foot valves, users need to clean the strainers themselves. However, some pumps have self-cleaning strainers. In these pumps, a small portion of pressurized liquid (like water) returns to the strainer through special piping. The liquid is then distributed to a series of special nozzles. The liquid sprays outward through the strainer at an angle. This spraying makes the screen rotate continuously. Consequently, any attached debris blows off the strainer and moves away from the suction line.
Foot valve maintenance tips
Properly maintain foot valves to ensure they work effectively and extend their lifespan. Below are some foot valve maintenance tips:
- Periodically check for debris in the strainer to ensure that it isn’t clogged. A clogged strainer affects water flow.
- Periodically check for signs of corrosion and wear in the foot valve. Corrosion can cause the valve to malfunction or leak. It might also cause backflow, especially if the disc is damaged.
- Ensure the bottom of the tank is clean at all times to prevent sediments from clogging the strainer.
Besides water pumps, many pneumatic systems use foot valves due to their ability to prevent fluid backflow and maintain the fluid column when the pump is off. Foot valves keep the pump primed in the following applications:
- HVAC systems
- Car wash systems
- Ponds, pools, and wells
- Irrigation systems
- Sump pumps and intake pumps in rivers and lakes
- Rural fire protection systems
- Pneumatic brake lines for commercial trucks
What is a foot valve, and how is it used?
A foot valve is a special type of non-return valve installed at the end of a pump suction in water or at the bottom of pipelines to prevent water from flowing backward when the pump is off.
What is the function of a strainer in a foot valve?
A strainer keeps out or filters debris, sediments, or solid particles that may come up from the suction line, clog or jam the foot valve, and damage the pump. It ensures efficient operation and a long lifespan of the valve.
How regularly should I clean the strainer?
Set up a routine maintenance check-up depending on factors such as the foot valve's workload, use, and how free your water is from debris.