A water tank pressure switch works by sensing the water pressure within the tank and activating or deactivating the well pump (or water pump) to maintain a specific pressure range.
Understanding the Components
- Pressure Tank: This tank holds a reserve of water under pressure. It's usually partially filled with air, which acts as a cushion.
- Pressure Switch: The device that monitors the water pressure and controls the pump. It's typically mounted on the pressure tank or close to it.
- Well Pump (or Water Pump): The pump that draws water from the well (or other source) and delivers it to the pressure tank.
The Working Principle
The process can be broken down into the following steps:
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Pressure Drop: When you use water in your home (e.g., flushing a toilet, taking a shower), water is drawn from the pressure tank. As the water level in the tank decreases, the air inside expands, and the water pressure drops.
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Activation Point (Cut-In Pressure): When the water pressure reaches a pre-set lower limit, known as the "cut-in" pressure, the pressure switch activates. This setting is usually adjustable within a certain range.
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Pump Activation: The pressure switch, acting as a simple on/off switch, closes the electrical circuit, powering on the well pump.
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Tank Filling: The well pump starts pumping water into the pressure tank. As water enters, the air inside the tank is compressed, causing the pressure to rise.
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Deactivation Point (Cut-Off Pressure): The pump continues to run until the water pressure reaches a pre-set upper limit, known as the "cut-off" pressure. Like the cut-in pressure, this is usually adjustable.
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Pump Deactivation: When the water pressure reaches the cut-off pressure, the pressure switch opens the electrical circuit, turning off the well pump.
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Cycle Repeats: The cycle repeats as water is used and the pressure drops again, restarting the pump at the cut-in pressure.
Pressure Switch Settings
Pressure switches are typically defined by two key pressure settings:
- Cut-In Pressure: The pressure at which the pump turns on.
- Cut-Off Pressure: The pressure at which the pump turns off.
A common setting is a 20 PSI cut-in and a 40 PSI cut-off (often written as 20/40). Other settings, such as 30/50 or 40/60, are also used. The range between these pressures dictates how much water is available before the pump needs to refill the tank.
Importance of Air Charge
The air charge in the pressure tank is crucial for proper operation. If the tank becomes waterlogged (loses its air cushion), the pump will cycle on and off frequently, which can shorten the lifespan of the pump and potentially damage the pressure switch. A properly charged tank extends the life of the pump by reducing the number of starts.
Troubleshooting
Common issues with pressure switches include:
- Pump not turning on: Could be a faulty switch, low water level in the well, or a problem with the pump itself.
- Pump not turning off: Could be a faulty switch, a leak in the plumbing system, or a waterlogged tank.
- Rapid cycling (short cycling): Usually indicates a waterlogged tank or a faulty switch.
