What is Foot Valve?
A foot valve is a type of check valve that only allows one-way flow. Use foot valves when you have situations that need a pump, such as when water needs to be extracted from an underground well. Foot valves keep the pump primed, allowing water to flow in, but not letting it flow back out, making them ideal for use in pools, ponds, and wells.
A foot valve is typically installed at a pump or at the bottom of a pipeline. Foot valves act like ball check valves but have an open end with a shield or screen over them to block debris from entering the line. The valve opening is designed to be larger than the line itself, minimizing head loss.
Foot valves can be found in ponds, pools and almost anywhere there is a pump. These special valves allow the pump to stay primed, letting the liquid flow in, but keeping it from flowing back out. The screens or baskets that cover the valve opening tend to get clogged over time, especially in ponds and wells. It is important to check and clean your valves regularly for optimum performance.
Construction of Foot Valve
Like most valves, foot valves come in a variety of materials. While each foot valve will be slightly different, the general design is universal. Look at this foot valve we’ve taken apart below. It consists of the main valve body and line connection, the ball, the seal carrier, the seal, and the screen. You’ notice that this valve can be fully disassembled for cleaning.
This particular model, which you can order direct from us, has a specially designed ball mechanism. This is not a standard sphere, but a weighted cup design that allows for superior functionality and durability. Unlike most ball-style valves, this valve ball will not spin in place or create worn areas that allow for leaks.
How Does Foot Valves Work?
As valves that only allow a unidirectional flow, foot valves open in one direction and close off when the direction of flow is reversed. That means that in applications like a well, the water can only be extracted out of the well. Any water that is remaining in the piping will not be allowed to flow backward through the valve toward the well.
Let’s take a look at the process a little more closely. In a shallow underground water well, the application of a foot valve involves the following:
- First, consider the placement of the foot valve. It is installed at the pick-up end of the piping (the end that is in the well, through which the water is extracted). It’s located near the bottom of the well.
- When the pump is operating, there is suction created that sucks the water up through the pipe. The foot valve opens as water flows upward because of the pressure from the incoming water.
- When the pump is shut off, the upward pressure stops. When this happens, gravity will go to work on the water that remains in the pipe, trying to cause it to move in a downward direction back into the well. However, the foot valve prevents that from happening.
- The weight of the water in the pipe pushes down on the foot valve. Because the foot valve is unidirectional, it doesn’t open in the downward directions. Instead, the pressure from the water closes the valve tightly, which prevents any reverse flow back into the well and from the pump back to the sump.
Why Are Foot Valves Needed?
Foot valves are beneficial because they prevent damage to water pumps that can occur due to dry runs, as well as stop wastage of energy.
These valves are a necessary part of all water pumping systems. The example above explains how the foot valve works on a very small scale. Consider the implications of not using a foot valve in larger, higher-volume situations.
In situations where water is being pumped from sumps on the ground to water tanks on top of buildings, it’s necessary to use powerful electric pumps. As an example, these pumps typically work by producing a suction that forces the water upward through the piping system to the desired tank.
While the pump is running, there’s a constant column of water in the pipe as a result of the suction that’s created. But when the pump is shut off, the suction disappears, and gravity affects the water column. If there wasn’t a foot valve in place, the water would flow down through the pipe, back to its original source. The pipe would be left empty of water, instead filled with air.
Then, when the pump is turned back on, the air that is in the pipe will oppose the flow of water, and even though the pump is on, water will not move through the pipe. When this happens, it causes dry runs, which can damage the pump if it isn’t addressed quickly.
The foot valve solves this problem effectively. It doesn’t allow any backflow of water when the pump is turned off. The pump stays primed for the next time it’s used.
How deep should a foot valve be?
The foot valve shall be installed a maximum of 25 feet vertical distance below the suction pipe of the pump inlet. The foot valve screen shall not be supported at the bottom of the tank or well for best operation efficiencies.
Uses for Foot Valves
Foot valves are check valves that are used with a pump. They are used in various different situations around the home and in some industrial applications as well. Foot valves may be used with pumps that are pumping liquids (called hydraulic pumps) like water, or in industrial applications, like gas (called a pneumatic pump).
Around the home, foot valves are used in ponds, pools, wells, and any other places where a pump is found. In industrial settings, these valves are used in sump pumps, intake pumps used in rivers and lakes, in the pneumatic brake lines of commercial trucks, and other applications where pumps are used. They are as effective in industrialized settings as they are in a backyard pond.
Foot valves are designed to keep the pump primed, allowing the liquid to flow in, but not out. There are screens that cover the valve opening that will become clogged after a period of time – especially when they are used to extract water from wells or in ponds. As a result, it’s important to clean valves regularly to keep them operating effectively.
Foot Valves Advantages
- These foot valves prevent damage to water pumps that can occur due to dry runs, as well as stopping wastage of energy.
- Without these foot valves, the water would flow downward through the pipe, back to its original source when the pump is shut off.
- Most of these valves are designed with self-tapping male and female threads to ensure easy installation.
- The internal balls ensure the quick sealing and valve reaction as well as flexibility to fit various types of water pump uses.
- They are cheaper to use, as compared to other valves used to prime a pump.
- Good quality foot valves help extend the overall lifespan of water pumps.
- They are cost-effective and lightweight.
