A foot valve is essential in submersible and jet pump systems, like wells. Submersible and jet pumps have foot valves on their intake suction line. Foot valves prevent water from flowing backwards when the pump is off and keep the pump primed. This article explores the various types and applications of foot valves.
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 reverse 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 the base of pipelines to stop water from flowing backwards when the pump is off. The valve keeps the liquid trapped in the suction pipe when the pump controls, thus sustaining a suitable height 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 a pump exists. The foot valve’s floor area or opening is larger than the pipe, minimizing head loss (energy dissipated due to friction along the pipe length). Since the filter 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.
Working
Based on the internal configuration, there are different types of foot valves, such as membrane, ball, and spring. 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 backwards. 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: The foot valve’s door or gateway 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 with 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, clog or jam the foot valve, and damage the pump. Filters are made from plastic, brass, or stainless steel. Plastic strainers are used in light-duty applications like small tanks. Stainless steel and brass filters are ideal for heavy-duty uses.
Cleaning the filter
For most foot valves, users need to clean the filters themselves. However, some pumps have self-cleaning strainers. A small portion of pressurized liquid (like water) in these pumps returns to the filter through special piping. The liquid is then distributed to a series of special nozzles. The liquid sprays outward through the filter at an angle. This spraying makes the screen rotate continuously. Consequently, any attached debris blows off the filter 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 filter to ensure it isn’t clogged. A clogged filter 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 always clean to prevent sediments from clogging the filter.
Applications
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
