What Is a Demand Pump and How Does It Work

A demand pump is a small pump that is activated when water is required and transports it from a storage tank to the point of usage in response. Generally, demand pumps are a simple, versatile, and cost-effective solution for controlling water flow in your home, garden, and more. For instance, when a faucet is turned on, the demand pump is operated and sends water through the open line as long as the faucet is running and consuming water. Similarly, the demand pump automatically shuts off when the faucet is turned off and the water demand has passed.

Put more simply, demand pumps transfer water from a storage tank to a distribution point. Also called delivery pumps, demand pumps rely on the user to pinpoint a water demand. Then, the user can activate a solenoid to open closed valves in the water line by pressing a button or lever to signal water requests. Demand pumps are designed to handle an array of fluid transfer operations, such as transferring water from a non-pressurized tank to a water fountain or providing a car wash with water on a bigger scale.

Users interested in installing a demand pump should also consider including a pump tank in their setup. The pump tank ensures that the right amount of steady back pressure is provided to the pump’s pressure switch, preventing the pump from cycling on and off to renew pressure. Furthermore, a pump tank offers an additional storage option and protects downstream appliances and plumbing applications from the shock of sudden pressure spikes.

Demand pumps work in two ways: demand and delivery. In a majority of cases, a demand pump will function in demand mode, and during this mode, a built-in pressure switch controls the pump. In contrast, pumps in delivery mode are controlled by an external switch, as opposed to a pressure switch incorporated within the pump. When water is needed, the switch is turned on manually, and the water is delivered by the delivery pump.

Essentially, demand pumps detect pressure changes and convey water as a result. To accomplish this, a solenoid valve opens when an appliance is turned on, signaling the demand pump that water is required. As previously mentioned, demand pumps have built-in pressure switches. For example, if a pump has a 65 psi pressure switch, the motor will run until the pressure in the line reaches the 65 psi shutoff setting. Before the motor is turned back on, these pressure switches drop anywhere between 10 and 15 psi. It is worth noting that a 65 psi shutdown switch will not reactivate until the pressure drops to 45 or 50 psi.

Found in a wide range of applications, demand pumps are useful anywhere that water must be transported from storage to the point of use. One such example is in their use alongside a storage tank of a reverse osmosis system to provide filtered water to faucets throughout a home. Moreover, demand pumps can be connected between a water filtration unit and a natural water source to store and distribute distilled water for individuals living off the grid or camping. They can also be used in hydroponic systems to circulate oxygenated and nutrient-rich water from storage to plants.

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