# How do I know what size expansion tank I need?

To determine what size expansion tank you need, you will need to consider the design of your system, the characteristics of the working fluid, and the potential for thermal expansion within the system.

You will want to calculate the total expansion volume for your system. This can be done by adding the hot water tank capacity to the water supply pipe from the pump plus any volume from connected distribution systems such as heating loops or recirculation lines.

Once you have the total expansion volume, you will want to calculate the additional volume needed to account for potential thermal expansion due to temperature changes. This can be done by calculating the working pressure of the system ( PSI ) and the coefficient of expansion of the working fluid.

You can then multiply the total expansion volume by the coefficient of expansion to get the additional volume needed. Finally, you should add the total expansion volume and the additional volume needed to get the total size of the expansion tank you will need.

It is important that the expansion tank you select is large enough to accommodate the total volume of thermal expansion in order to prevent damage to the system caused by excess pressure.

## What happens if expansion tank is too big?

If the expansion tank is too big it can cause a variety of problems. The most significant issue is that it will not be able to effectively absorb the expansion of the water in the system as temperatures fluctuate.

This can cause increased pressure on other parts of the system and result in a number of complications. These include leaks from the tank, damage to the internal components from the increased pressure, and corrosion of the internal parts.

Too much pressure can also increase the risk of premature failure in the system components. Additionally, an overly large expansion tank can create increased water consumption and decreased energy efficiency of the system.

## Will a bigger expansion tank increase water pressure?

No, a bigger expansion tank will not increase water pressure. An expansion tank is used to maintain water pressure in a closed-loop heating system, and serves as a cushion of air to absorb the increased volume of water created during the heating process.

Having a larger expansion tank may help to maintain a higher water pressure longer, but it will not increase the water pressure beyond the normal operating pressure of the system. The pressure of the water system is determined by the main water pressure regulator, located between the water meter and the main shut-off valve.

If the water pressure is too low, the regulator may have to be adjusted or replaced.

## What size expansion tank for 120 gallon water heater?

When it comes to sizing an expansion tank for a 120 gallon water heater, it will depend on several factors, such as the input water pressure, the temperature rating of the water heater, and the setting of the temperature and pressure relief valve.

Generally, you may want to get an expansion tank with a tank volume at least as large as the water heater. For a 120 gallon water heater, this would be approximately an 80 gallon expansion tank. However, it is always best to consult with a professional to determine the exact size and type of expansion tank that is best for your system.

## What can I use instead of a expansion tank?

An alternative to an expansion tank is a pressure reducing valve. This is designed to allow a preset, lower pressure to be maintained in the system when the pressure rises above the set level, then simply reduce the pressure back to the desired level.

This prevents pressure fluctuations and damage to the system, and can be more cost effective than an expansion tank. The primary downside is that a pressure reducing valve can not account for thermal expansion since it is a closed system, and thermal expansion can cause a system to overheat and eventually fail even with a pressure reducing valve in place.

## Why do expansion tanks explode?

Expansion tanks can explode when they are pressurized beyond their design specifications. This can be caused by a number of different factors, such as overcharging, a broken or sticking pressure relief valve, an increase in system pressure, or a corroded or malfunctioning tank.

An expansion tank that’s overcharged with an excessive amount of pressure can become swollen and burst, resulting in an explosion. The pressure of the tank should be no more than what’s specified by the manufacturer, typically between 10 and 15 psi (pounds per square inch).

Similarly, a malfunctioning pressure relief valve can cause excessive pressure buildup inside the tank, leading to an explosion.

Actual system pressure can also contribute to an expansion tank explosion, especially when the pressure increases suddenly, such as caused by a hot water heater. Lastly, rust, corrosion, and aging can damage the inner lining of the tank, and weaken the structural integrity of the metal vessel, leading to a potential explosion.

## How long does an expansion tank usually last?

The expected lifespan of an expansion tank depends on a few factors, such as the type of material used and the conditions in which it was installed. Most domestic tank-style expansion tanks made of steel or flexible diaphragm type have an expected lifespan of 10-15 years.

However, an expansion tank can last much longer when properly maintained. Regular inspection and tank draining are important to check for signs of corrosion or defects. Additionally, keeping the tank clean of dirt and sediment, as well as flushing it annually, can help extend its life.

## How often should an expansion tank be changed?

An expansion tank should be changed when it either reaches its maximum allowed pressure or if it has reached the end of its expected lifespan. The maximum pressure for an expansion tank is usually marked by the manufacturer on the side or bottom of the tank.

The expected lifespan of an expansion tank varies based on the quality of the tank, with higher quality tanks usually lasting much longer than lower quality tanks. In general, most high quality expansion tanks should last for around 10 years, with lesser quality tanks lasting for around 5 years.

It is important to remember that even if an expansion tank is working correctly, it should still be replaced periodically to ensure safe and efficient operation of your boiler system or other related plumbing equipment.

## Should you drain your expansion tank?

Whether or not you should drain your expansion tank depends on the type of system you have. Generally speaking, an open-vented heating system does not require draining, as the expansion tank acts as a receptacle for the expanding heated water and is refilled with cold water from the mains automatically as required.

However, if you have a sealed heating system, draining an expansion tank can help to reduce the pressure in your system, making it more efficient and preserving its longevity. If you choose to drain the tank, make sure you follow the manufacturer’s instructions, as the process can be hazardous if done incorrectly.

Consider first whether all other potential causes of a rise in pressure have been addressed and that the expansion vessel itself is in good condition. Whatever your system, it is best to have it serviced regularly to ensure everything is in good working order.

## Do expansion tanks go on hot or cold?

An expansion tank should go on the cold water side of a hydronic system such as a boiler, water heater, or other heating appliance. This tank is designed to allow excess pressure from the expanding hot water to be released, thus keeping the system from over-pressurizing.

Expansion tanks also reduce the amount of water lost to the atmosphere as steam. In a hydronic system, the cold side of the system does not normally see the same pressure fluctuations as the hot side, so it is the most appropriate place for the expansion tank.

If the expansion tank is installed on the hot side of the system, it can become constantly filled with steam and eventually fail.

In some cases, multiple expansion tanks are needed when a system is large or receives a large amount of water flow. These are typically installed in series, with the first one placed on the cold side of the system and the remaining tanks placed downstream on the hot side.

## Can you oversize an expansion vessel?

Yes, it is possible to oversize an expansion vessel. Oversizing an expansion vessel has its benefits, such as providing long-term protection from water hammer and preventing system damage if there is an increase in system pressure.

When an expansion vessel is too small for the system it can become overworked due to its inability to absorb the sudden changes in pressure. This can cause it to fail prematurely. Oversizing an expansion vessel ensures a surge in pressure is absorbed and security is maintained to the system.

However, it is important to note that while an expansion vessel can be oversized, this may actually cause its own set of problems. A vessel that is too large may not correctly react to pressure changes and cycles, thus ensuring that the benefits of its oversized structure are not realized.

Therefore, it is important to assess the required vessel size based on the system operation and design parameters.

## Can expansion tank cause overheating?

Expansion tanks can cause overheating in a few different ways. First, the expansion tank acts as an overflow reservoir for your vehicle’s cooling system. When the pressure in the cooling system becomes too high, the coolant is forced into the expansion tank.

This reduces the volume of coolant in the system, reducing its ability to absorb heat. If the volume remains low, the coolant will reach a higher temperature and the engine could overheat.

Expansion tanks can also cause overheating if they are full of air instead of coolant. When air fills the tank, it becomes difficult for the coolant to move from the radiator into the engine block, meaning the heat cannot be absorbed.

If the air remains trapped, it can drastically increase the temperature of the engine and cause it to overheat.

Finally, an expansion tank that is cracked or damaged can cause overheating. Cracks or damage means coolant can escape from the expansion tank, reducing the volume in the system and making it more difficult for the coolant to absorb heat.

If the coolant volume remains low, it can lead to the engine overheating.

In summary, expansion tanks can cause overheating if they are filled with air instead of coolant, have cracks or damage, or contain too much coolant. If any of these conditions are present, it is important to replace the expansion tank as soon as possible to reduce the risk of overheating.

## Can I oversize pressure tank?

Yes, it is possible to oversize a pressure tank, but it’s not always a good idea. Pressure tanks are designed to provide a sufficient amount of stored water so that a pump can draw it as needed. The size of the pressure tank is based on the rate of water use, meaning that if the tank is too large it won’t provide the necessary pressure to the pump.

An oversized pressure tank will also be unnecessarily expensive and take up more space than necessary. It is important to match the pressure tank size to the pump capacity and rate of water use in order to ensure optimal performance.

## Do I need a larger expansion tank?

Whether or not you need a larger expansion tank will depend on a number of factors, including the size of your home’s heating system and the type of system you have installed. As a rule of thumb, you should plan on needing a larger expansion tank if your system holds more than 65 gallons of water or if it has 8psi or greater of pressure.

Additionally, if your water heater has a tankless design or a steam-heat boiler, then you will definitely need a larger expansion tank.

It is important to keep in mind that expansion tanks are designed to help limit the amount of pressure within the home’s heating system. As a result, an expansion tank that is too small for the system can cause a number of issues, including short-cycling, water hammer, and even leaky water pipes.

Therefore, it is important to consult with a professional to determine the right size and type of expansion tank for your system.

## Should an expansion tank be on the cold or hot side?

The expansion tank, also known as a bladder tank or pressure tank, should be installed on the hot side of a hot water heater or boiler. This will provide a space for the expanding hot water to go when it is heated, instead of increasing the pressure in the pipes or releasing hot water into the cold lines.

The expansion tank is designed to absorb the increased pressure from the expanding hot water so the pressure levels in the plumbing system remain constant and the hot water heater or boiler does not release pressure from the relief valve to reduce the pressure.

If an expansion tank is not present, the hot water heater may experience significant damage due to overheating, leaks and possible failure of the relief valve. Additionally, without an expansion tank, there may be an increase in water heating costs and a decrease in system efficiency due to a decrease in the efficiency of the hot water heater.