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.
How 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 backwards 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 stopping 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. Like the 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 downward 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.
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.
Choosing the Right Foot Valve
There are many situations in which a foot valve is needed. Anytime there is an application that requires a one-way flow of liquid, a foot valve is necessary. Good quality foot valves help conserve energy and provide protection for water pumps from damage, extending their overall lifespan. Keep in mind that it’s important to use the best quality foot valve you can, as they can be challenging to access once they’re installed.
PVC foot valves are a good choice for most applications; they are cost-effective and lightweight. However, in applications that require temperatures or pressure that don’t allow for PVC, or that require specific chemical resistant materials, there are metal valve options like brass and stainless steel.