Understanding Pressure Tanks : Functionality, Types, and Applications

A pressure tank is a vital component in many water systems, designed to maintain consistent pressure and reduce the workload on water pumps. Whether in residential, commercial, or industrial applications, pressure tanks help ensure a steady flow of water and prevent frequent pump cycling, which can cause premature wear. The tank acts as a buffer, storing pressurized water that can be released when needed, making it essential for well water systems, fire suppression systems, and even some hydraulic systems.

In addition to enhancing the performance of water pumps, pressure tanks offer energy-saving benefits by minimizing the frequency of pump starts and stops. The technology behind pressure tanks has evolved, with different types such as diaphragm, bladder, and steel tanks being used for specific needs. Understanding how these tanks work, the types available, and their appropriate applications can help in selecting the right pressure tank for optimal system performance.

This article will explore how pressure tanks function, their types, common uses, and the factors to consider when choosing the right one for your system.

A pressure tank is a container used in various water and fluid systems to store and regulate pressurized liquid, most commonly water. Its primary function is to maintain consistent pressure within the system while reducing the workload on water pumps by minimizing the frequency of pump cycling.

Inside a pressure tank, there is usually a chamber for air and another for water, separated by a diaphragm or bladder. When water enters the tank, the air is compressed, creating pressure. As water is used or released from the system, the air pressure pushes the water out of the tank, ensuring a steady flow without requiring the pump to turn on every time water is needed. Once the pressure drops to a certain point, the pump activates to refill the tank and restore pressure.

Pressure tanks are used in a wide variety of applications:

• Residential water systems (such as well water systems)
• Irrigation systems
• Industrial water distribution
• Fire suppression systems

The pressure tank’s ability to regulate pressure and reduce pump cycling improves system efficiency and longevity, making it an essential component in many fluid-handling systems.

II. How Pressure Tanks Work

A pressure tank operates by storing water under pressure and releasing it when needed, ensuring consistent water pressure throughout the system while reducing the workload on the pump. The primary components of a pressure tank include a water chamber, an air chamber (or pre-pressurized air), and often a diaphragm or bladder that separates the two. Here’s a step-by-step breakdown of how pressure tanks function:

1. Initial Fill

• When the water system is turned on, the pump pushes water into the pressure tank.
• As water enters the tank, the air inside (either above or around the bladder/diaphragm) gets compressed, which creates pressure inside the tank.

2. Pressure Build-Up

• As more water enters, the air in the tank is further compressed, increasing the pressure.
• Most tanks come with a pre-set air pressure (typically 20-40 psi) that can be adjusted according to system requirements.
• When the pressure reaches a certain threshold (often 40-60 psi in residential systems), the pump automatically shuts off.

3. Water Release

• When water is drawn from the system (e.g., opening a faucet), the compressed air pushes the water out of the tank and into the pipes, providing consistent pressure without immediately needing the pump to run.
• As more water is used, the pressure inside the tank decreases.

4. Pressure Drop and Pump Activation

• Once the pressure drops to a pre-set low level (usually around 20-30 psi), the pump is triggered to refill the tank.
• The cycle of filling, pressurizing, and releasing repeats, ensuring that water pressure remains steady.

5. Bladder and Diaphragm Function

• In modern tanks, a flexible bladder or diaphragm separates the air and water, preventing the two from mixing. This feature reduces the risk of waterlogging, which occurs when the air inside the tank dissolves into the water, causing the pump to cycle more frequently.
• The bladder expands and contracts with the water flow, allowing for efficient pressure control without direct contact between air and water.

6. Pre-Set Pressure Control

• Pressure tanks are equipped with a pressure switch that regulates the pump operation based on the pressure inside the tank.
• The switch has upper and lower set points, so when the pressure drops to the lower limit, the pump starts, and when it reaches the upper limit, the pump stops.

III. Types of Pressure Tanks

Pressure tanks come in various types, each designed for specific applications and working conditions. These tanks differ in construction, functionality, and the way they manage the air and water pressure balance within a system. Here are the most common types of pressure tanks:

1. Diaphragm Pressure Tanks

• Construction: These tanks have a flexible diaphragm inside that separates the water from the air. The diaphragm flexes as water enters and exits the tank, compressing the air above it.
• How It Works: Water enters the tank below the diaphragm, and the air above it compresses as the tank fills, creating pressure. When water is drawn, the diaphragm pushes the water out of the tank, providing consistent pressure.
• Advantages:
  • No direct contact between water and air, reducing the risk of waterlogging (where air dissolves into the water).
  • Requires minimal maintenance.
• Disadvantages:
  • Over time, the diaphragm can wear out or rupture, requiring replacement.

2. Bladder Pressure Tanks

• Construction: These tanks contain a flexible bladder inside, which holds the water. The air surrounds the bladder and is compressed as the bladder expands when water fills the tank.
• How It Works: As water flows into the bladder, it expands, compressing the air around it. When water is used, the air pressure pushes the water out through the bladder.
• Advantages:
  • Excellent for maintaining water pressure.
  • Less prone to waterlogging due to the bladder separating air and water.
• Disadvantages:
  • The bladder can eventually deteriorate, requiring replacement.

3. Steel Pressure Tanks (Air-Over-Water)

• Construction: These tanks are made of steel and do not have a bladder or diaphragm. Instead, the water and air are stored directly inside the tank without separation.
• How It Works: Water and air share the same space. As water is pumped into the tank, it compresses the air, which creates pressure. When water is drawn, the air pushes the water out.
• Advantages:
  • Simple construction with fewer internal parts that could wear out.
  • Lower upfront cost.
• Disadvantages:
  • Air and water can mix over time, leading to waterlogging and frequent pump cycling.
  • Requires regular maintenance to replenish the air inside the tank.

4. Composite Pressure Tanks

• Construction: Composite tanks are made from lightweight, corrosion-resistant materials such as fiberglass or other synthetic materials. These tanks typically contain either a bladder or diaphragm inside.
• How It Works: Similar to diaphragm and bladder tanks, water enters a chamber inside the tank, compressing air within the composite shell.
• Advantages:
  • Lightweight and resistant to rust and corrosion.
  • Durable and long-lasting, making them ideal for harsh environments.
• Disadvantages:
  • Higher cost compared to steel tanks.
  • Limited to specific applications that justify the added cost.

5. Hydropneumatic Tanks

• Construction: These tanks are designed for larger systems and may or may not include a bladder or diaphragm. They are often used for applications requiring high water capacity, such as industrial settings or large residential systems.
• How It Works: The tank stores a large volume of water and uses compressed air to maintain pressure. These tanks can be either bladderless or equipped with a bladder, depending on the design.
• Advantages:
  • Suitable for large water systems with significant demand.
  • Can handle higher water volumes and pressures.
• Disadvantages:
  • More complex and expensive than smaller residential tanks.
  • Requires routine maintenance to ensure proper pressure and air balance.

6. In-Line Pressure Tanks

• Construction: These are smaller tanks designed for installation directly in the water supply line, often in point-of-use applications.
• How It Works: In-line tanks are compact and store a small amount of pressurized water, helping to regulate pressure in specific areas of the system.
• Advantages:
  • Ideal for limited space or point-of-use systems.
  • Reduces pressure spikes and smooths out water flow in smaller applications.
• Disadvantages:
  • Limited water storage capacity.
  • May not be suitable for larger systems requiring more water

Each type of pressure tank serves a specific purpose, depending on the needs of the system, such as the size of the system, required water pressure, and maintenance considerations. Diaphragm and bladder tanks are often the preferred choice for residential and small commercial systems due to their reliability and efficiency. Steel tanks, though less efficient, may be more affordable but require more maintenance, while composite and hydropneumatic tanks cater to larger systems with higher demands.

IV. Applications of Pressure Tanks

Pressure tanks play a crucial role in maintaining consistent water pressure and optimizing the performance of various water systems. Their versatility makes them essential in a wide range of applications, from household water systems to industrial processes. Here are some common applications of pressure tanks:

1. Residential Water Supply Systems

• Well Water Systems: Pressure tanks are an integral part of well water systems. They store water from the well and deliver it to household taps with consistent pressure. The tank reduces the need for the well pump to run continuously, extending its lifespan and minimizing energy usage.
• Irrigation Systems: In homes with gardens or irrigation systems, pressure tanks help ensure steady water pressure for sprinklers and hoses, providing efficient watering without frequent pump cycling.
• Rainwater Harvesting: Pressure tanks can also be used in rainwater harvesting systems to regulate water pressure when rainwater is used for household purposes like irrigation or toilet flushing.

2. Commercial and Industrial Water Systems

• Commercial Water Distribution: Pressure tanks are used in large buildings and commercial facilities to maintain water pressure for plumbing systems, ensuring that water reaches all floors and taps with adequate pressure.
• Industrial Fluid Handling: Pressure tanks are common in industries that rely on fluid transfer, including manufacturing, chemical processing, and food and beverage production. They help regulate the pressure of fluids being pumped through systems, ensuring smooth operation.
• Boiler Systems: In heating systems with boilers, pressure tanks are used to maintain the proper water pressure, allowing the system to function efficiently while preventing pressure surges or drops that could damage equipment.

3. Fire Suppression Systems

• Pressure tanks are often used in fire suppression systems to provide a reliable source of pressurized water in case of emergencies. These tanks store water under pressure, ensuring immediate availability for firefighting purposes without waiting for pumps to engage.

4. Hydraulic Systems

• In hydraulic systems, pressure tanks (or hydropneumatic tanks) help regulate fluid pressure, acting as accumulators. This is particularly important in industries that rely on hydraulic machinery, such as construction, mining, and manufacturing. Pressure tanks reduce pressure fluctuations and ensure smooth and stable hydraulic system operation.

5. Water Treatment Systems

• Reverse Osmosis Systems: In water treatment, pressure tanks are used in reverse osmosis (RO) systems to store filtered water under pressure. This ensures that purified water is readily available when needed without putting strain on the filtration system.
• Water Softening Systems: Pressure tanks can also be employed in water softening systems, providing a consistent supply of softened water for household or industrial use.

6. Agricultural Applications

• Livestock Watering: Farms and agricultural operations often rely on pressure tanks to maintain water pressure for livestock watering systems. These tanks ensure a steady supply of water to drinking stations for animals, even in remote areas without municipal water access.
• Pumping Water for Irrigation: Pressure tanks are vital in agricultural irrigation systems where water is pumped from wells, reservoirs, or rivers. They regulate water pressure for sprinklers or drip irrigation, ensuring even distribution of water across fields.

7. Pressure Booster Systems

• In areas where water pressure is too low to meet demand, pressure tanks are used in conjunction with booster pumps to increase water pressure. This is particularly useful in high-rise buildings, commercial complexes, or locations with low municipal water pressure.

8. Marine and RV Water Systems

• Pressure tanks are frequently used in marine vessels and recreational vehicles (RVs) to regulate water pressure for onboard plumbing. The tank ensures a steady flow of water for sinks, showers, and toilets without continuously running the water pump, conserving energy and pump life.

9. Geothermal and Solar Hot Water Systems

• In geothermal and solar hot water systems, pressure tanks play an essential role in maintaining water pressure and ensuring the system operates efficiently. The tank helps regulate the flow of water heated by solar panels or geothermal sources, preventing pressure surges or drops.

10. Compressed Air Systems

• While pressure tanks are most commonly associated with water systems, they can also be used in compressed air systems. Air pressure tanks store and regulate compressed air in applications such as industrial pneumatic tools, spray painting, and even some HVAC systems.

Pressure tanks have diverse applications across residential, commercial, industrial, and agricultural systems. Their ability to maintain consistent water or fluid pressure, reduce pump cycling, and provide immediate pressurized water or air makes them indispensable in a variety of settings. Whether you’re maintaining a household water system or regulating industrial fluid transfer, pressure tanks play a vital role in ensuring the smooth and efficient operation of these systems.

V. Sizing and Choosing a Pressure Tank

Selecting the right pressure tank for your system is crucial to ensure proper water pressure, reduce pump cycling, and extend the lifespan of the pump. Several factors must be considered, such as the system’s water demand, pump size, and pressure requirements. Here’s a guide to help you properly size and choose a pressure tank:

1. Understanding Tank Sizing

• The size of a pressure tank is determined by its capacity to store water and maintain adequate pressure in the system. Tank size is typically measured in gallons, which indicates the total volume of water the tank can hold.
• The drawdown capacity—the actual amount of water available between pump cycles—is the key metric for sizing a tank. Drawdown depends on the tank’s size, the pressure settings, and the system’s pressure range.
  • For example, in a system set to operate between 30 psi (cut-in) and 50 psi (cut-off), the drawdown capacity will vary based on the tank’s overall volume.

2. Factors to Consider in Sizing

• Household or System Water Usage: The higher the water usage, the larger the pressure tank needed. Systems with frequent water use (like large households, farms, or commercial buildings) require a larger tank to store more pressurized water.
• Pump Flow Rate: The pump’s flow rate, typically measured in gallons per minute (GPM), helps determine the size of the tank. A general rule of thumb is to have one gallon of drawdown capacity for each GPM the pump produces.
  • Example: For a 10 GPM pump, you need a tank with at least 10 gallons of drawdown capacity.
• Pressure Settings: The difference between the cut-in and cut-off pressure (i.e., the range in which the pump turns on and off) affects the drawdown capacity. Systems with a wider pressure range require less frequent cycling and may allow for smaller tanks.
• Pump Cycling: To minimize wear on the pump, you want the pump to cycle fewer times per hour. A larger tank will allow more water to be drawn before the pump needs to refill, reducing the number of cycles.

3. Calculating the Right Size

• Flow Rate Formula: A common formula to size a pressure tank is to multiply the flow rate (GPM) by the desired minimum runtime for the pump (in minutes). A typical pump should run for at least 1 to 2 minutes per cycle.
  • Formula: $$\text{Tank Size (Gallons)}=\text{Flow Rate (GPM)}\times \text{Minimum Run Time (Minutes)}$$
  • Example: For a pump with a 10 GPM flow rate and a desired runtime of 2 minutes, the tank should have a capacity of: $$10\text{GPM}\times 2\text{Minutes}=20\text{Gallons}$$
• Drawdown Capacity Calculation: The drawdown capacity can be determined using the pump’s cut-in and cut-off pressure settings. Most tank manufacturers provide drawdown tables based on these settings.

4. Types of Pressure Tanks to Consider

• Diaphragm and Bladder Tanks: These tanks offer more efficient water storage and are less prone to waterlogging, making them suitable for most residential and small commercial systems. They come in various sizes to fit specific needs.
• Steel Pressure Tanks: These are larger, traditional tanks that require regular air replenishment and are typically used for older or larger systems. They can store more water but may require more maintenance.
• Composite Tanks: Lightweight and corrosion-resistant, these are ideal for systems that need durable, long-lasting tanks, especially in environments prone to rust or corrosion.

5. Pressure Tank Sizing Chart (Example)

Here’s an example of typical tank sizes based on pump flow rates:

6. Choosing the Right Material

• Steel Tanks: Ideal for heavy-duty or high-demand systems but susceptible to rust without proper treatment.
• Fiberglass or Composite Tanks: More resistant to corrosion, these are ideal for areas with corrosive water or harsh environments. They are lighter and easier to install but can be more expensive.
• Stainless Steel Tanks: Suitable for food-grade or medical applications where hygiene is important, as they resist contamination and corrosion.

7. Pressure Rating Considerations

• Pressure tanks come with specific pressure ratings, such as 30-50 psi or 40-60 psi. Ensure the pressure rating matches your system’s pump cut-in and cut-off pressures.
• Adjusting Pressure Settings: It’s important to adjust the tank’s pre-charge (air pressure) to approximately 2 psi below the pump’s cut-in pressure to ensure the system works efficiently.

8. Maintenance and Lifespan

• When selecting a pressure tank, consider how much maintenance the tank will require over its lifetime. Diaphragm and bladder tanks typically need less maintenance than steel tanks.
• Most pressure tanks last between 5 and 15 years, depending on the material, quality, and how well they are maintained.

Properly sizing and choosing a pressure tank is essential for maintaining system efficiency, reducing pump wear, and ensuring consistent water pressure. By considering factors such as pump flow rate, water usage, pressure settings, and tank material, you can select a tank that meets the needs of your residential, commercial, or industrial water system. Always ensure the tank is large enough to handle the system’s demands while minimizing the pump’s workload for extended lifespan and optimal performance.

VI. Advantages of Pressure Tanks

Pressure tanks offer several benefits, making them indispensable in various residential, commercial, and industrial water systems. By helping to regulate water pressure, reduce pump cycling, and improve efficiency, pressure tanks provide numerous advantages that enhance the overall performance of a water system. Here are some key advantages:

1. Consistent Water Pressure

• One of the primary functions of a pressure tank is to maintain consistent water pressure throughout the system. The tank stores pressurized water and releases it when needed, ensuring a steady flow of water to faucets, showers, and appliances. This prevents fluctuations in water pressure that can occur when relying solely on the pump to deliver water.
• Consistent pressure is especially important in systems with varying demand, such as homes with multiple bathrooms or irrigation systems.

2. Reduced Pump Cycling

• Pressure tanks help reduce the frequency of pump cycling, which is the process of the pump turning on and off as water is used. By storing a certain amount of pressurized water, the pump does not need to activate every time a small amount of water is drawn from the system.
• This leads to fewer pump cycles, which extends the lifespan of the pump by reducing wear and tear.
• Fewer pump starts also save energy, reducing operational costs.

3. Energy Efficiency

• By minimizing the number of times the pump has to run, pressure tanks contribute to energy savings. The pump consumes a significant amount of energy each time it starts up, and by reducing how often it operates, the system becomes more energy-efficient.
• In systems with high water demand, this can lead to significant reductions in energy bills over time.

4. Prevention of Water Hammer

• Water hammer is the sudden pressure surge or spike that occurs when a valve closes abruptly in a pipeline, causing loud banging noises and potential damage to the pipes and fittings. Pressure tanks help mitigate water hammer by regulating pressure and providing a buffer in the system.
• This reduces the stress on pipes and valves, preventing damage and prolonging the lifespan of the plumbing infrastructure.

5. Pump Longevity

• Pumps are designed to run efficiently over long periods, but frequent starting and stopping (cycling) can wear them out quickly. By storing pressurized water and reducing the frequency of pump operation, pressure tanks help protect the pump from excessive wear, extending its operational life.
• This leads to lower maintenance costs and less frequent pump replacements, making pressure tanks a cost-effective addition to any system.

6. Improved Water Availability

• Pressure tanks ensure that water is readily available whenever needed. The tank acts as a reservoir, storing a certain amount of water that can be drawn immediately without waiting for the pump to activate. This is especially useful in systems where there may be a delay in water supply when relying solely on a pump.
• In systems with variable water demand, such as irrigation or fire suppression systems, pressure tanks ensure that there is always a buffer of water ready for use.

7. Versatility

• Pressure tanks are versatile and can be used in a variety of applications, including residential water systems, industrial fluid handling, agricultural irrigation, and hydraulic systems. Their ability to maintain pressure and reduce pump cycling makes them valuable across many industries and settings.
• In addition to water systems, pressure tanks can also be used in compressed air systems, providing pressure regulation for pneumatic tools and equipment.

8. Corrosion Resistance (With Certain Materials)

• Many pressure tanks, especially those made from composite or fiberglass materials, are resistant to rust and corrosion, making them ideal for use in areas with harsh water conditions or where metal tanks may degrade over time.
• This increases the durability and lifespan of the tank, reducing the need for frequent replacements and lowering maintenance costs.

9. Protection Against Power Outages

• In systems where the pump requires electricity to operate, a pressure tank provides a temporary water reserve in the event of a power outage. The pressurized water stored in the tank can be used until the power is restored or until an alternative power source is engaged.
• This feature is particularly beneficial in rural areas or locations prone to power disruptions.

10. Minimizes Water Waste

• Pressure tanks help minimize water waste by ensuring that water is delivered consistently and efficiently. Without a pressure tank, water systems may experience surges and drops in pressure, leading to inefficient water use. A pressure tank ensures that water is available when needed without excessive or wasteful pumping.

Pressure tanks offer numerous advantages, from improving water pressure consistency to reducing pump cycling and enhancing energy efficiency. Their ability to protect pumps from wear, prevent water hammer, and provide water availability during outages makes them an essential component of any well-functioning water system. Whether for residential, industrial, or agricultural use, pressure tanks help maintain the reliability and performance of fluid-handling systems, offering long-term cost savings and improved system longevity.

VII. Conclusion

Pressure tanks are vital components in various water and fluid systems, providing significant benefits such as maintaining consistent pressure, reducing pump cycling, and improving overall system efficiency. Whether in residential water supplies, industrial operations, or agricultural irrigation, these tanks play an essential role in ensuring a steady flow of water and protecting pumps from excessive wear. By minimizing energy consumption, preventing water hammer, and offering immediate access to pressurized water, pressure tanks not only extend the life of pumps but also deliver cost savings in the long run.

Choosing the right size and type of pressure tank is crucial to ensure optimal performance. Proper sizing based on water demand and pump capacity is key to maximizing efficiency and ensuring reliable system operation. With advancements in materials and designs, pressure tanks today are more durable, versatile, and resistant to corrosion, making them suitable for a wide range of applications.

In summary, pressure tanks are a cost-effective, energy-saving, and performance-enhancing solution for managing water pressure in various systems. Investing in the right pressure tank can significantly improve the functionality and longevity of your water system, making it a worthwhile addition to any setup.