A pressure tank works on a water pump by storing water under pressure, providing it to your plumbing system when the pump isn't actively running, and minimizing the pump's on/off cycles. This extends the life of your pump and provides a more consistent water supply.
Here's a breakdown of the process:
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Initial State: The pressure tank contains both air and water, separated by a diaphragm or bladder. The air is pre-charged to a specific pressure (usually around 2 PSI below the pump's cut-in pressure).
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Pump Operation & Water Filling: When water is used and the pressure in the tank drops to a pre-set "cut-in" pressure, the water pump turns on. As the pump runs, it forces water into the tank, compressing the air inside.
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Pressure Buildup: As water fills the tank, the air compresses, increasing the pressure within the tank. This pressurized air provides the force needed to push water out to your fixtures (faucets, showers, etc.) even before the pump turns on again.
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Pump Shut-off: The pump continues to run until the pressure inside the tank reaches a pre-set "cut-off" pressure (typically around 40-60 PSI). At this point, a pressure switch signals the pump to turn off.
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Water Delivery from Tank: When you open a faucet or use water, the pressurized air inside the tank pushes the stored water out into your plumbing system. The pump does not need to turn on immediately because you're using the reserve of pressurized water in the tank.
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Cycle Repeat: As water is drawn from the tank, the pressure gradually decreases. When the pressure drops to the "cut-in" point, the pump turns on again, restarting the cycle.
Why this is beneficial:
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Extends Pump Life: By storing water under pressure, the pressure tank significantly reduces the number of times the pump has to start and stop. Starting a pump requires a lot of energy and creates wear and tear. Fewer cycles mean a longer lifespan for the pump.
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Consistent Water Pressure: The pressure tank helps maintain more consistent water pressure throughout your home. You're not solely reliant on the pump's immediate output, which can fluctuate.
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Water Hammer Prevention: The air cushion within the tank helps absorb pressure surges (water hammer) caused by suddenly turning faucets on or off. This protects your pipes from damage.
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Water Reserve: Provides a small reserve of water for immediate use, especially during times of peak demand.
Simplified Analogy:
Think of the pressure tank as a balloon that's half-filled with air and half-filled with water. When you squeeze the balloon (the pump adding water), the air compresses and provides pressure. When you let go (turn on a faucet), the compressed air pushes the water out.
