A foot valve is a component used with a pump to help the pump stay primed, ensuring that when people turn it on, it will immediately begin pumping water. Foot valves are found in wells, attached to pool cleaners, and in other settings where fluids are being pumped. The valve allows the pump to be turned on and off without concerns about whether the pump will stay primed and it also filters fluids pulled into the line to reduce the risk of clogs.
Foot valves are a form of check valve, a valve that only admits flow in one direction. In the case of a foot valve, fluid can be pulled into the valve and up the line, but it cannot flow back out. When the pump is on, water moves through the valve, into the line, and into the pump itself. When the pump is turned off, the water in the line stays in place because the valve prevents it from flowing backward. If the water was allowed to drain out of the line, air would end up in the line and the pump would need to be primed again to get it flowing.
A typical foot valve is covered with a basket or cage. The cage keeps detritus in the well out of the valve so that it cannot get into the line. Over time, the holes in the cage can become clogged and it may be necessary to haul the line up and clean them. This can be a bigger problem in areas where people routinely come close to the bottom of their wells, as muck and debris settle at the bottom of the well and will be churned up by pumping in the dry season.
These devices are usually hidden from view, making it difficult for people to determine when they need cleaning and maintenance. The head is deliberately designed large to ensure a smooth flow of water, but if the water becomes sluggish or dirty, it can be a sign that there is something wrong with the foot valve and it needs to be pulled up for inspection.
Brass, plastic, and other noncorrosive materials are favored for the construction of a foot valve. These materials are durable and will last for a long time. They also tend to be more expensive to work with and consequently foot valves tend to be pricey. When purchasing a foot valve, buyers weigh the initial cost against the valve's expected life. Many companies offer extended guarantees for their products, assuring consumers that they will replace valves if they fail unexpectedly.